  Exploration of superconductivity in light element compounds has drawn
considerable attention because those materials can easily realize the high
$T_{c}$ superconductivity, such as
${\mathrm{LnNi}}_{2}{\mathrm{B}_{2}}{\mathrm{C}}$ ($T_{c}$ =17 K),
${\mathrm{Mg}}{\mathrm{B}}_{2}$ ($T_{c}$ =39 K), and very recently
super-hydrides under pressure ($T_{c}$ =250 K). Here we report the discovery of
bulk superconductivity at 7.8 K in scandium borocarbide
${\mathrm{Sc}}_{20}{\mathrm{B}}{\mathrm{C}}_{27}$ with a tetragonal lattice
which structure changes based on the compound of
${\mathrm{Sc}}_{3}{\mathrm{C}}_{4}$ with very little B doping. Magnetization
and specific heat measurements show bulk superconductivity. An upper critical
field of Hc2(0) ~ 8 T is determined. Low temperature specific-heat shows that
this system is a BCS fully gapped s-wave superconductor. Electronic structure
calculations demonstrate that compared with ${\mathrm{Sc}}_{3}{\mathrm{C}}_{4}$
there are more orbital overlap and hybridization between Sc 3d electrons and 2p
electrons of C-C(B)-C fragment in
${\mathrm{Sc}}_{20}{\mathrm{B}}{\mathrm{C}}_{27}$, which form a new electric
conduction path of Sc-C(B)-Sc. Those changes influence the band structure at
the Fermi level and may be the reason of superconductivity in
${\mathrm{Sc}}_{20}{\mathrm{B}}{\mathrm{C}}_{27}$.
