  A theory of twisted (and other structured) paraxial electrons in a uniform
magnetic field is developed. The obtained general quantum-mechanical solution
of the relativistic paraxial equation contains the commonly accepted result as
a specific case of unstructured electron waves. In the weak-field limit, our
solution (unlike the existing theory) is consistent with the well-known
equation for free twisted electron beams. The observable effect of a different
behavior of relativistic Laguerre-Gauss beams with opposite directions of the
orbital angular momentum penetrating from the free space into a magnetic field
is predicted. Distinguishing features of the quantization of the velocity and
the effective mass of structured electrons in the uniform magnetic field are
analyzed.
