Exhibit 10.5


 


October 27, 2021


 


Seaport Calibre Materials Acquisition Corp.

360 Madison Avenue

20th Floor

New York, NY 10017


 


Re: Initial Public Offering


 


Ladies and Gentlemen:


 


This letter (this “Letter Agreement”)
is being delivered to you in accordance with the Underwriting Agreement (the “Underwriting Agreement”) entered
into by and among Seaport Calibre Materials Acquisition Corp., a Delaware corporation (the “Company”), and Seaport
Global Securities LLC, as representative (the “Representative”) of the several underwriters (each, an “Underwriter”
and collectively, the “Underwriters”), relating to an underwritten initial public offering (the “Public
Offering”), of 13,000,000 of the Company’s units (including up to 1,950,000 units that may be purchased
to cover over-allotments, if any) (the “Units”), each comprised of one share of the Company’s Class A
common stock, par value $0.0001 per share (the “Common Stock”), and one-half of one redeemable warrant.
Each whole warrant (each, a “Warrant”) entitles the holder thereof to purchase one share of Common Stock at
a price of $11.50 per share, subject to adjustment as described in the Prospectus. The Units will be sold in the Public Offering
pursuant to a registration statement on Form S-1 and prospectus (the “Prospectus”) filed by the Company
with the U.S. Securities and Exchange Commission (the “Commission”) and the Company has applied to have
the Units listed on The Nasdaq Capital Market. Certain capitalized terms used herein are defined in paragraph 11 hereof.


 


In order to induce the Company and the Underwriters
to enter into the Underwriting Agreement and to proceed with the Public Offering and for other good and valuable consideration, the receipt
and sufficiency of which are hereby acknowledged, each of Seaport Global Asset Management, LLC (“SGAM”), Calibre
Group, LLC (“Calibre” (collectively the “Sponsors”) and the undersigned individuals,
each of whom is a member of the Company’s board of directors and/or management team or an Initial Stockholder (each, an “Insider”
and collectively, the “Insiders”), hereby agrees with the Company as follows:


 


1.                  
Each of the Sponsors and each Insider agrees that if the Company seeks stockholder approval of a proposed Business Combination,
then in connection with such proposed Business Combination, it, he or she shall (i) vote any shares of Capital Stock owned by it,
him or her in favor of any proposed Business Combination and (ii) not redeem any shares of Common Stock owned by it, him or her in
connection with such stockholder approval. If the Company engages in a tender offer in connection with any proposed Business Combination,
each of the Sponsors and each Insider agrees that it, he or she will not seek to sell its, his or her shares of Capital Stock to the Company
in connection with such tender offer.


 


2.                   Each
of the Sponsors and each Insider hereby agrees that in the event that the Company fails to consummate a Business Combination
within 15 months from the closing of the Public Offering (or up to 18 months as described in the Prospectus), or
such later period approved by the Company’s stockholders in accordance with the Company’s amended and restated
certificate of incorporation (the “Charter”), the Sponsors and each Insider shall take all reasonable
steps to cause the Company to (i) cease all operations except for the purpose of winding up, (ii) as promptly as
reasonably possible but not more than 10 business days thereafter, subject to lawfully available funds therefor,
redeem 100% of the shares of Common Stock sold as part of the Units in the Public Offering (the “Offering
Shares”), at a per-share price, payable in cash, equal to the aggregate amount then on deposit in the Trust Account
(as defined below), including interest earned on the funds held in the Trust Account and not previously released to the Company to
pay its taxes (less up to $100,000 of interest to pay dissolution expenses), divided by the number of then outstanding Offering
Shares, which redemption will completely extinguish all Public Stockholders’ rights as stockholders (including the right to
receive further liquidation distributions, if any), subject to applicable law, and (iii) as promptly as reasonably possible
following such redemption, subject to the approval of the Company’s remaining stockholders and the Company’s board of
directors, dissolve and liquidate, subject in each case to the Company’s obligations under Delaware law to provide for claims
of creditors and other requirements of applicable law. Each of the Sponsors and each Insider agrees not to propose any amendment to
the Charter to modify the substance or timing of the ability of holders of Offering Shares to seek redemption in connection with a
Business Combination or the Company’s obligation to redeem 100% of the Offering Shares if the Company does not complete a
Business Combination within such time set forth in the Charter, unless the Company provides its public stockholders with the
opportunity to redeem their Offering Shares upon approval of any such amendment at a per-share price, payable in cash, equal to the
aggregate amount then on deposit in the Trust Account, including interest earned on the funds held in the Trust Account and not
previously released to the Company to pay its taxes, divided by the number of then outstanding Offering Shares.


 






     


     


    

 


Each of the Sponsors and each Insider acknowledges
that it, he or she has no right, title, interest or claim of any kind in or to any monies held in the Trust Account or any other asset
of the Company as a result of any liquidation of the Company with respect to the Founder Shares held by it, him or her. Each of the Sponsors
and each Insider hereby further waives, with respect to any shares of Common Stock held by it, him or her, if any, any redemption rights
it, he or she may have in connection with the consummation of a Business Combination, including, without limitation, any such rights available
in the context of a stockholder vote to approve such Business Combination or a stockholder vote to approve an amendment to the Charter
to modify the substance or timing of the Company’s obligation to redeem 100% of the Offering Shares if the Company has not
consummated a Business Combination within the time period set forth in the Charter or in the context of a tender offer made by the Company
to purchase Offering Shares (although the Sponsors, the Insiders and their respective affiliates shall be entitled to redemption and liquidation
rights with respect to any Offering Shares it or they hold if the Company fails to consummate a Business Combination within the time period
set forth in the Charter).


 


3.                  
During the period commencing on the date of the Underwriting Agreement and ending 180 days after such date, the Sponsors
and each Insider shall not (i) sell, offer to sell, contract or agree to sell, grant any option to sell (including any short sale),
transfer, hypothecate, pledge, grant any option to purchase or otherwise dispose of or agree to dispose of, directly or indirectly, or
establish or increase a put equivalent position or liquidate or decrease a call equivalent position within the meaning of Section 16
of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and the rules and regulations
of the Commission promulgated thereunder, with respect to any Units, shares of Capital Stock, Warrants or any securities convertible into,
or exercisable, or exchangeable for, shares of Capital Stock currently or hereafter owned either of record or beneficially by it, him
or her, (ii) enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences
of ownership of any Units, shares of Capital Stock, Warrants or any securities convertible into, or exercisable, or exchangeable for,
shares of Capital Stock currently or hereafter owned either of record or beneficially by it, him or her, whether any such transaction
is to be settled by delivery of such securities, in cash or otherwise, or (iii) publicly announce any intention to effect any transaction
specified in clause (i) or (ii).


 


4.                  
In the event of the liquidation of the Trust Account upon the failure of the Company to consummate its initial Business Combination
within the time period set forth in the Charter, the Sponsors (the “Indemnitor”) agree to indemnify and hold
harmless the Company against any and all loss, liability, claim, damage and expense whatsoever (including, but not limited to, any and
all legal or other expenses reasonably incurred in investigating, preparing or defending against any litigation, whether pending or threatened)
to which the Company may become subject as a result of any claim by (i) any third party for services rendered or products sold to
the Company or (ii) any prospective target business with which the Company has entered into a written letter of intent, confidentiality
or other similar agreement or Business Combination agreement (a “Target”); provided, however, that such indemnification
of the Company by the Indemnitor shall (x) apply only to the extent necessary to ensure that such claims by a third party or a Target
do not reduce the amount of funds in the Trust Account to below the lesser of (i) $10.00 per Offering Share and (ii) the actual
amount per Offering Share held in the Trust Account as of the date of the liquidation of the Trust Account, if less than $10.00 per
Offering Share is then held in the Trust Account due to reductions in the value of the trust assets, less interest earned on the Trust
Account which may be withdrawn to pay taxes, (y) not apply to any claims by a third party or a Target which executed a waiver of
any and all rights to the monies held in the Trust Account (whether or not such waiver is enforceable) and (z) not apply to any claims
under the Company’s indemnity of the Underwriters against certain liabilities, including liabilities under the Securities Act of 1933,
as amended. The Indemnitor shall have the right to defend against any such claim with counsel of its choice reasonably satisfactory to
the Company if, within 15 days following written receipt of notice of the claim to the Indemnitor, the Indemnitor notifies the
Company in writing that it shall undertake such defense.


 


5.                   To
the extent that the Underwriters do not exercise their over-allotment option to purchase up to an additional 1,950,000 Units
within 45 days from the date of the Prospectus (and as further described in the Prospectus), the Sponsors and other
Initial Stockholders agree to forfeit, at no cost, a number of Founder Shares in the aggregate equal to 487,500 multiplied by a
fraction, (i) the numerator of which is 1,950,000 minus the number of Units purchased by the Underwriters upon the
exercise of their over-allotment option, and (ii) the denominator of which is 1,950,000. The Sponsors and other Initial
Stockholders will be required to forfeit only that number of Founder Shares as is necessary so that the Initial Stockholders will
own an aggregate of 20.0% of the Company’s issued and outstanding shares of Capital Stock after the Public Offering.


 






     


     


    

 


6.                  
(a)Each Insider may become an officer or director of another special purpose acquisition company with a class of securities
intended to be registered under the Exchange Act, even before the Company has entered into a definitive agreement regarding an initial
Business Combination.


 


(b)               
Each of the Sponsors and each Insider hereby agrees and acknowledges that: (i) the Underwriters and the Company would be irreparably
injured in the event of a breach by such Sponsors or an Insider of its, his or her obligations under paragraphs 1, 2, 3, 4, 5, 7(a),
7(b), and 9, as applicable, of this Letter Agreement (ii) monetary damages may not be an adequate remedy for such breach and
(iii) the non-breaching party shall be entitled to injunctive relief, in addition to any other remedy that such party may have in
law or in equity, in the event of such breach.


 


7.                  
(a)Each of Sponsors, together with their controlled affiliates, and each Insider agrees that it, he or she shall not cause
any Founder Shares (including, specifically, the 115,494 Founder Shares held by Stephen Smith) (or shares of Common Stock issuable
upon conversion thereof) to be sold during the offering, or sold, transferred, assigned, pledged, or hypothecated, or be the subject of
any hedging, short sale, derivative, put or call transaction that would result in the economic disposition of such securities until the
later of: (i) after the 180-day period immediately following commence of sales of the Public Offering, subject to certain exceptions
permitted by FINRA Rule 5110(e)(2), and (ii) the earlier of (A) one year after the completion of the Company’s initial
Business Combination or (B) subsequent to the Business Combination, (x) if the last sale price of the Common Stock equals or
exceeds $12.00 per share (as adjusted for stock splits, stock dividends, reorganizations, recapitalizations and the like) for any 20
trading days within any 30-trading day period commencing at least 150 days after the Company’s initial Business Combination
or (y) the date on which the Company completes a liquidation, merger, capital stock exchange, reorganization or other similar transaction
that results in all of the Company’s stockholders having the right to exchange their shares of Common Stock for cash, securities
or other property (the “Founder Shares Lock-up Period”).


 


(b)               
Each of Sponsors, together with their controlled affiliates, and each Insider agrees that it, he or she shall not cause any Private
Placement Warrants (including, specifically, the 2,536,667 and 233,333 Private Placement Warrants acquired by SGAM and Stephen
Smith, respectively) (or shares of Common Stock issued or issuable upon the exercise of the Private Placement Warrants), to be sold during
the offering, or sold, transferred, assigned, pledged, or hypothecated, or be the subject of any hedging, short sale, derivative, put
or call transaction that would result in the economic disposition of such securities until the later of (i) 30 days after the completion
of a Business Combination, or (ii) in compliance with FINRA Rule 5110(e), to the extent such date falls within the 180-day
period immediately following commencement of sales of the Offering, the end 180-day period immediately following commencement of
sales of the Offering, subject to certain exceptions permitted by FINRA Rule 5110(e)(2). (the “Private Placement Warrants
Lock-up Period”, together with the Founder Shares Lock-up Period, the “Lock-up Periods”).


 


(c)                 Notwithstanding
the provisions set forth in paragraphs 7(a) and (b), Transfers of the Founder Shares, Private Placement Warrants, any private
placement warrants issued upon conversion of working capital loans (“Working Capital Warrants”) and shares
of Common Stock issued or issuable upon the exercise or conversion of the Private Placement Warrants, Working Capital Warrants or
the Founder Shares and that are held by the Sponsors, any Insider or any of their permitted transferees (that have complied with
this paragraph 7(c)), are permitted (i) to the Company’s officers or directors, any affiliates or family members of
any of the Company’s officers or directors, any members of the Company’s Initial Stockholders, or any affiliates of the
Initial Stockholders; (ii) in the case of an individual, by gift to a member of one of the members of the individual’s
immediate family or to a trust, the beneficiary of which is a member of one of the individual’s immediate family, an affiliate
of such person or to a charitable organization; (iii) in the case of an individual, by virtue of laws of descent and
distribution upon death of the individual; (iv) in the case of an individual, pursuant to a qualified domestic relations order;
(v) by private sales or transfers made in connection with the consummation of an initial Business Combination at prices no
greater than the price at which the shares or warrants were originally purchased; (vi) in the event of the Company’s
liquidation prior to the completion of the Company’s initial Business Combination; (vii) by virtue of the laws of
Delaware or the Sponsors’ limited liability company agreement upon dissolution of the Sponsors; or (viii) in the event of
the Company’s liquidation, merger, capital stock exchange, reorganization or other similar transaction which results in all of
the Company’s stockholders having the right to exchange their shares of Common Stock for cash, securities or other property
subsequent to Company’s completion of the initial Business Combination; provided, however, that notwithstanding the foregoing,
compliance with FINRA Rules 5110(e) and 5110(g) shall be maintained at all times, and in the case of clauses (i)
through (v) or (vii) these permitted transferees must enter into a written agreement with the Company agreeing to be bound
by these transfer restrictions and the other restrictions contained herein.


 






     


     


    

 


8.                  
Each of the Sponsors and each Insider represents and warrants that it, he or she has never been suspended or expelled from membership
in any securities or commodities exchange or association or had a securities or commodities license or registration denied, suspended
or revoked. Each Insider’s biographical information furnished to the Company (including any such information included in the Prospectus)
is true and accurate in all respects and does not omit any material information with respect to the Insider’s background. Each Insider’s
questionnaire furnished to the Company is true and accurate in all respects. Each Insider represents and warrants that: it, he or she
is not subject to or a respondent in any legal action for, any injunction, cease-and-desist order or order or stipulation to desist or
refrain from any act or practice relating to the offering of securities in any jurisdiction; it, he or she has never been convicted of,
or pleaded guilty to, any crime (i) involving fraud, (ii) relating to any financial transaction or handling of funds of another
person, or (iii) pertaining to any dealings in any securities and it, he or she is not currently a defendant in any such criminal
proceeding.


 


9.                  
Except as disclosed in the Prospectus, neither the Sponsors nor other Initial Stockholder, nor any officer, nor any affiliate of
the Sponsors nor Initial Stockholders nor any officer, nor any director of the Company, shall receive from the Company any finder’s
fee, reimbursement, consulting fee, monies in respect of any repayment of a loan or other compensation prior to, or in connection with
any services rendered in order to effectuate, the consummation of the Company’s initial Business Combination (regardless of the
type of transaction that it is).


 


10.               
The Sponsors and each Insider has full right and power, without violating any agreement to which it is bound (including, without
limitation, any non-competition or non-solicitation agreement with any employer or former employer), to enter into this Letter Agreement
and, as applicable, to serve as an officer and/or director on the board of directors of the Company and hereby consents to being named
in the Prospectus as an officer and/or director of the Company.


 


11.               
As used herein,


 


(a)                
“Business Combination” shall mean a merger, capital stock exchange, asset acquisition, stock purchase,
reorganization or similar business combination, involving the Company and one or more businesses;


 


(b)               
“Capital Stock” shall mean, collectively, the Common Stock and the Founder Shares;


 


(c)                
“Founder Shares” shall mean the 4,312,500 shares of Class B Common Stock held by the Sponsors
and other Initial Stockholders;


 


(d)               
“Initial Stockholders” shall mean the Sponsors and any Insider that holds Founder Shares;


 


(e)                
“Private Placement Warrants” shall mean the Warrants to purchase up to 4,700,000 shares of Common
Stock of the Company (up to 5,090,000 if the over-allotment option is exercised in full) that the Sponsors certain controlled affiliates
of SGAM have committed to subscribe to purchase in sum for an aggregate purchase price of $7,050,000 (up to $7,635,000 if the over-allotment
option is exercised in full), or $1.50 per Warrant, in a private placement that shall occur simultaneously with the consummation
of the Public Offering;


 


(f)                 
“Public Stockholders” shall mean the holders of securities issued in the Public Offering;


 









     


     


    

 


(g)               
 “Trust Account” shall mean the trust fund into which a portion of the net proceeds of the Public Offering
shall be deposited; and


 


(h)               
“Transfer” shall mean the (i) sale of, offer to sell, contract or agreement to sell, hypothecate,
pledge, grant of any option to purchase or otherwise dispose of or agreement to dispose of, directly or indirectly, or establishment or
increase of a put equivalent position or liquidation with respect to or decrease of a call equivalent position within the meaning of Section 16
of the Exchange Act, and the rules and regulations of the Commission promulgated thereunder with respect to, any security, (ii) entry
into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of any
security, whether any such transaction is to be settled by delivery of such securities, in cash or otherwise, or (iii) public announcement
of any intention to effect any transaction specified in clause (i) or (ii).


 


12.               
The Company will maintain an insurance policy or policies providing directors’ and officers’ liability insurance, and
each officer and director shall be covered by such policy or policies, in accordance with its or their terms, to the maximum extent of
the coverage available for any of the Company’s directors or officers.


 


13.               
This Letter Agreement constitutes the entire agreement and understanding of the parties hereto in respect of the subject matter
hereof and supersedes all prior understandings, agreements, or representations by or among the parties hereto, written or oral, to the
extent they relate in any way to the subject matter hereof or the transactions contemplated hereby. This Letter Agreement may not be changed,
amended, modified or waived (other than to correct a typographical error) as to any particular provision, except by a written instrument
executed by all parties hereto.


 


14.               
No party hereto may assign either this Letter Agreement or any of its rights, interests, or obligations hereunder without the prior
written consent of the other parties. Any purported assignment in violation of this paragraph shall be void and ineffectual and shall
not operate to transfer or assign any interest or title to the purported assignee. This Letter Agreement shall be binding on the Sponsors
and each Insider and their respective successors, heirs and assigns and permitted transferees.


 


15.               
Nothing in this Letter Agreement shall be construed to confer upon, or give to, any person or corporation other than the parties
hereto any right, remedy or claim under or by reason of this Letter Agreement or of any covenant, condition, stipulation, promise or agreement
hereof. All covenants, conditions, stipulations, promises and agreements contained in this Letter Agreement shall be for the sole and
exclusive benefit of the parties hereto and their successors, heirs, personal representatives and assigns and permitted transferees.


 


16.               
This Letter Agreement may be executed in any number of original or facsimile counterparts and each of such counterparts shall for
all purposes be deemed to be an original, and all such counterparts shall together constitute but one and the same instrument.


 


17.               
This Letter Agreement shall be deemed severable, and the invalidity or unenforceability of any term or provision hereof shall not
affect the validity or enforceability of this Letter Agreement or of any other term or provision hereof. Furthermore, in lieu of any such
invalid or unenforceable term or provision, the parties hereto intend that there shall be added as a part of this Letter Agreement a provision
as similar in terms to such invalid or unenforceable provision as may be possible and be valid and enforceable.


 


18.               
This Letter Agreement shall be governed by and construed and enforced in accordance with the laws of the State of New York, without
giving effect to conflicts of law principles that would result in the application of the substantive laws of another jurisdiction. The
parties hereto (i) all agree that any action, proceeding, claim or dispute arising out of, or relating in any way to, this Letter
Agreement shall be brought and enforced in the courts of New York City, in the State of New York, and irrevocably submit to such jurisdiction
and venue, which jurisdiction and venue shall be exclusive and (ii) waive any objection to such exclusive jurisdiction and venue
or that such courts represent an inconvenient forum.


 









     


     


    

 


19.               
 Any notice, consent or request to be given in connection with any of the terms or provisions of this Letter Agreement shall be
in writing and shall be sent by express mail or similar private courier service, by certified mail (return receipt requested), by hand
delivery or facsimile transmission.


 


20.               
This Letter Agreement shall terminate on the earlier of (i) the expiration of the Lock-up Periods or (ii) the liquidation
of the Company; provided, however, that this Letter Agreement shall earlier terminate in the event that the Public Offering is not consummated
and closed by December 31, 2021; provided further that paragraph 4 of this Letter Agreement shall survive such liquidation.


 


21.               
The Company, each of the Sponsors and each Insider hereby acknowledges and agrees that the Representative on behalf of the Underwriters
is a third party beneficiary of this Letter Agreement.


 


[Signature Page Follows]


 






     


     


    

 





	 	Sincerely,
	 	 
	 	SGAM Sponsor Sub, LLC
	 	 
	 	By:	/s/ Steve Smith
	 	Name: Steve Smith
	 	Title: CEO of Managing Member
	 	 
	 	Calibre Sponsor Sub, LLC
	 	 
	 	By:	/s/ Jim Tumulty
	 	Name: Jim Tumulty
	 	Title: Co-Manager of Managing Member
	 	 
	 	By:	/s/ Steve Smith
	 	Name: Steve Smith
	 	 
	 	By:	/s/ Jim Tumulty
	 	Name: Jim Tumulty
	 	 
	 	By:	/s/ Ed Siegel
	 	Name: Ed Siegel
	 	 
	 	By:	/s/ Patrick Murley
	 	Name: Patrick Murley
	 	 
	 	By:	/s/ Shawn Tumulty
	 	Name: Shawn Tumulty
	 	 
	 	By:	/s/ Robert McMaster
	 	Name: Robert McMaster
	 	 
	 	By:	/s/ Lee Mueller
	 	Name: Lee Mueller




 


Acknowledged and Agreed:


 


[Signature Page to Letter Agreement]


 









     


     


    

 


	SEAPORT CALIBRE MATERIALS
 ACQUISITION CORP.
	 
	By:	/s/ Jim Tumulty
	 	Name: Jim Tumulty
	 	Title: Chief Executive Officer






 


[Signature Page to Letter Agreement]