Angle-dependent magnetoresistance oscillations and magnetic breakdown in α-(BEDT-TTF)2KHg(SCN)4

We present results of stereographic measurements of interlayer magnetoresistance in the quasi-two-dimensional (Q2D) organic conductor, α-(BEDT-TTF)2KHg(SCN)4, at around charge density wave (CDW) transition temperature Tc∼8K. At 2 K in the CDW phase, there exists the anomalous Lebed resonance pattern, the amplitude of which is modulated by Danner-Chaikin oscillations in case of applied magnetic field close to the Q2D conducting plane. On the contrary, at 7 K just below Tc, we have found that the Kajita oscillation of the cylindrical Fermi surfaces appears superposed on the anomalous Lebed resonance. A quantum model of interlayer tunneling demonstrates these behaviors qualitatively. These results suggest that magnetic breakdown plays a key role in anomalous angle-dependent magnetoresistance oscillations.