UNCONVENTIONAL MAGNETIC-FIELD AND PRESSURE DEPENDENCES OF THE GROUND-STATE OF THE LOW-DIMENSIONAL ORGANIC SUPERCONDUCTOR (BEDO-TTF)(2)REO4-CENTER-DOT-H2O

Magnetotransport experiments have been carried out in the two-dimensio nal organic metal (BEDO-TTF)(2)ReO4 . H2O at temperatures down to 0.4 K and under hydrostatic pressure up to 11 kbar. When measured in magne tic field of a few teslas, the magnetoresistance is large and a steep resistance rise is observed below 4 K, which, as is the case for quasi -one-dimensional TMTSF-based compounds, is the signature of a spin den sity wave condensation. As already observed at ambient pressure, two s eries of Shubnikov-de Haas oscillations, linked to hole and electron o rbits, are evidenced in the applied pressure range from 3.5 to 11 kbar . Both hole and electron orbit; oscillation frequencies (respectively noted F-h and F-e) increase strongly as the pressure increases (dln(F- h,F-e)/dP = 0.07 kbar(-1)), while their ratio remains unchanged (F-h/F -e = 2). As the applied pressure increases, both cyclotron masses eith er slowly decrease or remain constant, keeping low values when compare d to other 2D compounds.