  The Shubnikov - de Haas effect in quasi-two-dimensional normal metals is
studied. The interlayer conductivity is calculated using the Kubo formula. The
electron scattering on short-range is considered in the self-consistent Born
approximation. The result obtained differs from that derived from the Boltzmann
transport equation. This difference is shown to be a general feature of
conductivity in magnetic field. A detailed description of the two new
qualitative effects -- the field-dependent phase shift of beats and of the slow
oscillations of conductivity is provided. The results obtained are applicable
to strongly anisotropic organic metals and to other quasi-two-dimensional
compounds.
