  We study the effects of the Zeeman term on the de Haas van Alphen (dHvA)
oscillation in two-dimensional two-band systems. We found that the Fourier
transform amplitudes of the oscillations are not described by the spin
reduction factor in the Lifshitz-Kosevich formalism in two-dimensional systems.
The anomalous dependence on the effective $g$-factor can be observed by
tilting-angle dependence of the dHvA oscillation in quasi-two-dimensional
organic conductors and Sr$_2$RuO$_4$.

Mesoscale and Nanoscale Physics