  We explore the Dirac equation in external electromagnetic and torsion fields.
Motivated by the previous study of quantum field theory in an external torsion
field, we include a nonminimal interaction of the spinor field with torsion. As
a consequence, the torsion axial vector and the electromagnetic potential enter
the action in a similar form. The existence of an extra local symmetry is
emphasized and the Foldy-Wouthuysen transformation is performed to an accuracy
of next to the leading order. We also discuss the motion of a classical test
particle in a constant torsion field.
