  Carter derived the forms of the metric and the vector potentials of the
space-times in which the relativistic Schrodinger equation for the motion of a
charged particle separates. Here we show that on each `spheroidal' surface a
rotation rate exists such that relative to those rotating axes the electric and
magnetic fields are parallel and orthogonal to the spheroid which is thus an
equipotential in those axes. All the finite Carter separable systems without
magnetic monopoles or gravomagnetic NUT monopoles have the same gyromagnetic
ratio as the Dirac electron.
