  We consider a recently derived kinetic model for weakly relativistic quantum
plasmas. We find that that the effects of spin-orbit interaction and Thomas
precession may alter the linear dispersion relation for a magnetized plasma in
case of high plasma densities and/or strong magnetic fields. Furthermore, the
ponderomotive force induced by an electromagnetic pulse is studied for an
unmagnetized plasma. It turns out that for this case the spin-orbit interaction
always give a significant contribution to the quantum part of the ponderomotive
force.
