  ${\rm SU}(2|1)$ supersymmetric multi-particle quantum mechanics with
additional semi-dynamical spin degrees of freedom is considered. In particular,
we provide an $\mathcal{N}{=}\,4$ supersymmetrization of the quantum ${\rm
U}(2)$ spin Calogero-Moser model, with an intrinsic mass parameter coming from
the centrally-extended superalgebra $\widehat{su}(2|1)$. The full system admits
an ${\rm SU}(2|1)$ covariant separation into the center-of-mass sector and the
quotient. We derive explicit expressions for the classical and quantum ${\rm
SU}(2|1)$ generators in both sectors as well as for the total system, and we
determine the relevant energy spectra, degeneracies, and the sets of physical
states.
