Fermi surface studies of tbe pressure induced organic superconductor (BEDT-TTF)/sub 3/Cl/sub 2/.2H/sub 2/O

Summary form only given. We present Fermi surface studies of the organic superconductor, (BEDT-TTF)/sub 3/Cl/sub 2/.2H/sub 2/O, in the pressure range 10-20 kbar, temperature range 700 mK-4.2 K and in magnetic fields up to 17 T. Superconductivity is observed above 700 mK in the pressure range 10-14.5 kbar and is accompanied by a single series of Shubnikov-de Haas oscillations, corresponding to ca. 0.5-1% of the first Brillouin zone. The frequency increases monotonically from 45 T at 12.5 kbar to 100 T at 20 kbar. The mass of the carriers obtained from fitting the temperature dependence of the amplitude of the Fourier transform to the Lifshitz-Kosevich model, is roughly pressure independent. The value of 0.8 m/sub e/ obtained is low for such materials; in other BEDT-TTF salts we have observed enhancement from the electronic band mass which has been associated with strong electron correlations in these narrow band conductors. Results of the present study will be discussed in relation to the crystal and electronic band structures and the Hall resistance, thermopower, susceptibility and optical reflectivity.