EX-10.5





 Exhibit 10.5 

EXECUTION VERSION 

ALTIMAR ACQUISITION CORP. III 

40 West 57th Street 
 33rd Floor

 New York, New York 10019 

March 3, 2021 
 Altimar Sponsor III, LLC

 40 West 57th Street 
 33rd Floor 

New York, New York 10019 
 Ladies and Gentlemen: 

This letter will confirm our agreement that, commencing on the effective date (the “Effective Date”) of the
registration statement on Form S-1 (the “Registration Statement”) for the initial public offering (the “IPO”) of the securities of Altimar Acquisition Corp. III,
a Cayman Islands exempted company (the “Company”), and continuing until the earlier of (i) the consummation by the Company of an initial business combination and (ii) the Company’s liquidation (in each case, as
described in the Registration Statement) (such earlier date hereinafter referred to as the “Termination Date”), Altimar Sponsor III, LLC, a Delaware limited liability company (the “Sponsor”), shall
take steps directly or indirectly to make available to the Company, at 40 West 57th Street, 33rd Floor, New York, New York 10019 (or any successor location), office space and secretarial and administrative services as may be required by the Company
from time to time. In exchange therefor, the Company shall pay the Sponsor a sum of $10,000 per month on the Effective Date and continuing monthly thereafter until the Termination Date. The Sponsor hereby agrees that it does not have any right,
title, interest or claim of any kind (a “Claim”) in or to any monies that may be set aside in a trust account that may be established upon the consummation of the IPO (the “Trust Account”) and hereby
irrevocably waives any Claim it may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek recourse against the Trust Account for any reason whatsoever. 

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 amended, modified or waived as to any particular provision, except by a written instrument executed by the
parties hereto. 
 The parties may not assign this letter agreement or any of their respective rights, interests or obligations hereunder
without the consent of the other party. 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 governed by, construed in accordance with and interpreted pursuant to the laws of the State of New York. 












 This letter agreement may be executed in one or more counterparts, each of which shall for
all purposes be deemed to be an original but all of which together shall constitute one and the same agreement. Only one such counterpart signed by the party against whom enforceability is sought needs to be produced to evidence the existence of
this letter agreement. 
 [Signature Page Follows] 

  
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	Sincerely,
	
	ALTIMAR ACQUISITION CORP. III
		
	By:	 	 /s/ Tom Wasserman

		 	Name: Tom Wasserman
		 	Title: Chief Executive Officer


  

			
	AGREED AND ACCEPTED BY:
	
	ALTIMAR SPONSOR III, LLC
		
	By:	 	 /s/ Faith Rosenfeld

		 	Name: Faith Rosenfeld
		 	Title: Chief Administrative Officer

 [Signature Page to Administrative Support Agreement—Altimar Acquisition Corp. III]