High Pressure and High Field Studies of α-[(CH3)2(C2H5)2N][Ni(dmit)2]2

The magnetoresistance of α-[(CH3)2(C2H5)2N][Ni(dmit)2]2 has been studied at ambient pressure in magnetic fields of up to 60 T and under hydrostatic pressures of up to 6 kbar in fields of up to 17 T. The high field measurements indicate a very simple Fermi surface. Measurements in medium fields, however, indicate several quantum oscillation frequencies, whose weight gets reduced with increasing field in favour of the major γ-orbit. The low field α- and β-orbits exhibit a strong pressure sensitivity. Whereas no quantum oscillations were observed at 2 kbar, shifted α-and β-frequencies occur at a pressure of 6 kbar.