  Theory of magneto-oscillation phenomena has been developed for
two-dimensional electron systems with linear-in-k spin splitting. Both
Dresselhaus and Rashba contributions are taken into account. It has been shown
that the pattern of the magneto-oscillations depends drastically on the ratio
between the above terms. The presence of only one type of the k-linear terms
gives rise to the beats, i.e. two close harmonics corresponding to the
spin-split subbands. However, if the strengths of both contributions are
comparable, the third (central) harmonics appears in the spectrum of the
magneto-oscillations. For equal strengths of the contributions, only the
central harmonic survives, and the oscillations occur at a single frequency,
although the k-linear terms remain in the Hamiltonian. Such suppression of the
spin beats is studied in detail by the example of the Shubnikov-de Haas effect.
