  We investigate the nonrelativistic limit of the gravitationally coupled Dirac
Equation via a Foldy-Wouthuysen transformation. The relativistic correction
terms have immediate and obvious physical interpretations in terms of a
gravitational zitterbewegung, and a gravitational spin-orbit coupling. We find
no direct coupling of the spin vector to the gravitational force, which would
otherwise violate parity. The particle-antiparticle symmetry described recently
by one of us in [Phys.Rev.A 87 (2013) 032101] is verified on the level of the
perturbative corrections accessed by the Foldy-Wouthuysen transformation. The
gravitational corrections to the electromagnetic transition current are
calculated.
