We briefly review some of the recent high-field de Haas-van Alphen (dH
vA) results we obtained for the quasi-two-dimensional organic metals a
nd superconductors of the type alpha-(ET)(2)X, where ET (=BEDT-TTF) is
bis(ethylenedithio)-tetrathiafulvalene and X is a monovalent anion. W
e further report on new dHvA, Shubnikov-de Haas, and specific-heat res
ults for the recently synthesized organic superconductor beta''-(ET)(2
)SF5CH3CF2SO3 (T-c = 4.5 K). The Fermi-surface topology, the possible
influence of the low dimensionality on the quantum oscillations, and t
he influence of many-body interactions are discussed. The results indi
cate the importance of electron-phonon interaction and point towards s
trong coupling. (C) 1998 Elsevier Science B.V. All rights reserved.