The effects of magnetic ordering of the localized 4f electrons in rare earth metals on the structure of the Brillouin zones in these metals, and hence on the conduction-electron characteristics, are studied by means of a magneticsuperlattice model. The model takes into account the exchange interaction between the 4f and conduction electrons, and effects of spin-orbit interactions of the 4f electrons. The model is used to study the electric resistivity of Er and Tb as functions of crystal orientation amd applied magnetic field. (T.F.H.)