  For a spin-1/2 particle moving in a background magnetic field in
noncommutative phase space, Dirac equation is solved when the particle is
allowed to move off the plane that the magnetic field is perpendicular to. It
is shown that the motion of the charged particle along the magnetic field has
the effect to increase the magnetic field. In the classical limit, matrix
elements of the velocity operator related to the probability give a clear
physical picture: Along an effective magnetic field the mechanical momentum is
conserved and the motion perpendicular to the effective magnetic field follows
a round orbit. If using the velocity operator defined by the coordinate
operators, the motion becomes complicated.
