QUANTUM OSCILLATIONS OF MAGNETORESISTANCE IN A NEW ORGANIC SUPERCONDUCTOR (BEDT-TTF)2(NH4)HG(SCN)4

Magnetotransport studies have been carried out in a new organic superconductor (BEDT-TTF)2(NH4)Hg(SCN)4 [bis(ethylenedithiolo)-tetrathiafulvalenium mercuric ammonium thiocyanate] using pulsed high magnetic fields up to 35T. We observed both the large Shubnikovda Haas (SdH) oscillations and the angle-dependent quantum oscillations. The experimental results suggest the existence of a cylindrical Fermi surface with weak warping. Its cross-sectional area parallel to the conducting plane is estimated from the SdH period Δ(1/B) = 0.0018 T-1 as 13% of that of the first Brillouin zone. Compared to the isostructual compound (BEDT-TTF)2KHg(SCN)4 which shows anomalous magnetotransport features, this compound shows very normal behaviours as expected in typical quasi-two-dimensional systems. © 1990.