CSISD[p] can be used as input for D-1-dimensional with D-1-dimensional Cartesian vector p and is transformed into PauliSigma[CartesianMomentum[p,D-1],D-1] by FeynCalcInternal.
[p] CSISD
[p] // FCI // StandardForm
CSISD
(*PauliSigma[CartesianMomentum[p, -1 + D], -1 + D]*)
[p, q, r, s] CSISD
[p, q, r, s] // StandardForm
CSISD
(*CSISD[p] . CSISD[q] . CSISD[r] . CSISD[s]*)