Abstract
Functions are defined as products of a properly symmetrized function for a free electron in a magnetic field and of a Bloch-type function. An equation is derived for the Bloch-type function, and it is shown that in general the energy for a Bloch electron in a magnetic field is obtained by superimposing Landau levels on the energy spectrum of the crystal. The treatment is based on the symmetry of the equation for a Bloch electron in magnetic field.