The $\Gamma$-matrices are built-in, albeit undocumented. This is the Internal`DiracGammaMatrix command.
The are 3 choices for the basis of the matrices, namely chiral, Dirac and Majorana. From the above choices, the chiral basis is the default.
Table[Internal`DiracGammaMatrix[k, "Basis" -> "Chiral"] //
MatrixForm, {k, 4}]
Table[Internal`DiracGammaMatrix[k] // MatrixForm, {k, 4}]

Table[Internal`DiracGammaMatrix[k, "Basis" -> "Dirac"] //
MatrixForm, {k, 4}]

Table[Internal`DiracGammaMatrix[k, "Basis" -> "Majorana"] //
MatrixForm, {k, 4}]

MatrixForm /@Table[Internal`DiracGammaMatrix[k, "Basis" -> "Chiral"], {k, 4}]. Likewise for the other two choices – bmf Feb 06 '23 at 00:47