  Starting from the Dirac equation in external electromagnetic and torsion
fields we derive a path integral representation for the corresponding
propagator. An effective action, which appears in the representation, is
interpreted as a pseudoclassical action for a spinning particle. It is just a
generalization of Berezin-Marinov action to the background under consideration.
Pseudoclassical equations of motion in the nonrelativistic limit reproduce
exactly the classical limit of the Pauli quantum mechanics in the same case.
Quantization of the action appears to be nontrivial due to an ordering problem,
which needs to be solved to construct operators of first-class constraints, and
to select the physical sector. Finally the quantization reproduces the Dirac
equation in the given background and, thus, justifies the interpretation of the
action.
