DEHAASVANALPHEN EFFECT IN KAPPA-(DMET)2AUBR2

We have performed magnetization measurements of the title compound up to 12 tesla and down to 0.5 K in order to examine the Fermi-surface to pology. The de Haas-van Alphen effect has been clearly observed. This is the first report on the quantum oscillation in kappa-phase compound other than the BEDT-TTF salts. The oscillation has two components wit h different frequencies. The faster one corresponds just to the cross- sectional area of the 1 st Brillouin zone and the other to 21 % of tha t. Such a cross-sectional profile of the Fermi surface is essentially the same as in the kappa-phase of BEDT-TTF compounds. However, the sim ultaneous oscillation even at low field in this system is different fr om the result for kappa-(BEDT-TTF)2Cu(NCS)2, where the faster oscillat ion is reported to occur only at higher field as a magnetic breakdown effect. The present result implies that kappa-(DMET)2AuBr2 has no gap against the crossing of the Fermi surface at the zone boundary unlikel y kappa-(BEDT-TTF)2Cu(NCS)2. This comes from the difference in the spa ce group of the two crystals. The effective mass for each orbit is est imated.