Local flattening of the Fermi surface and cyclotron resonance in a normal magnetic field in cadmium and zinc

It is shown that resonance singularities of the surface impedance, observed in monocrystalline samples of cadmium /V. P. Naberezhnykh and N. K. Dan’shin, Zh. Eksp. Teor. Fiz. 56, 1223 (1969)/ and zinc /V. P. Naberezhnykh and V. L. Mel’nik, Fiz. Tverd. Tela (St. Petersburg) 7, 258 (1965)/ in a magnetic field H directed along the normal to the metal may be caused for H‖n‖[1122¯0] by local flattening of the Fermi surface at the vertices of an electron lens.