  The experimental results obtained for the magneto-transport in the
InGaAs/InAlAs double quantum wells (DQW) structures of two different shapes of
wells are reported. The beating-effect occurred in the Shubnikov-de Haas (SdH)
oscillations was observed for both types of the structures at low temperatures
in the parallel transport when magnetic field was perpendicular to the layers.
An approach to the calculation of the Landau levels energies for DQW structures
was developed and then applied to the analysis and interpretation of the
experimental data related to the beating-effect. We also argue that in order to
account for the observed magneto-transport phenomena (SdH and Integer Quantum
Hall effect), one should introduce two different quasi-Fermi levels
characterizing two electron sub-systems regarding symmetry properties of their
states, symmetric and anti-symmetric ones which are not mixed by
electron-electron interaction.
