Anomalous beating phase of the oscillating interlayer magnetoresistance in layered metals

We analyze the beating behavior of the magnetic quantum oscillations in a layered metal under the conditions when the cyclotron energy $\hbar \omega_c$ is comparable to the interlayer transfer energy $t$. We find that the positions of the beats in the interlayer resistance are considerably shifted from those in the magnetization oscillations, and predict that the shift is determined by the ratio $\hbar \omega_c/t$. A comparative study of the Shubnikov-de Haas and de Haas-van Alphen effects in the quasi-two-dimensional organic metal $\beta$-(BEDT-TTF)$_2$IBr$_2$ appears to be consistent with the theoretical prediction.