  The interplay between angular and quantum magnetoresistance oscillations in
quasi-two-dimensional metals leads to the angular oscillations of the amplitude
of quantum oscillations. This effect becomes pronounced in high magnetic field,
when the simple factorization of the angular and quantum oscillations is not
valid. The amplitude of quantum magnetoresistance oscillations is reduced at
the Yamaji angles, i.e. at the maxima of the angular magnetoresistance
oscillations. These angular beats of the amplitude of quantum oscillations
resemble and may be confused with the spin-zero effect, coming from the Zeeman
splitting. The proposed effect of "false spin zeros" becomes stronger in the
presence of incoherent channels of interlayer electron transport and can be
used to separate the different contributions to the Dingle temperature and to
check for violations from the standard factorization of angular and quantum
magnetoresistance oscillations.
