QUASI-2-DIMENSIONAL SPIN-SPLIT FERMI-LIQUID BEHAVIOR OF KAPPA-(BEDT-TTF)(2)I-3 IN STRONG MAGNETIC-FIELDS

Measurements of both the magnetization and magnetotransport of kappa-( BEDT-TTF)(2)I-3 (BEDT-TTF is bisethylenedithio-tetrathiafulvalene) in magnetic fields extending to 60 T at 0.4 K and 20 T at 35 mK are repor ted. Strong eddy currents observed in the magnetization are found to e xhibit critical currentlike behavior. This might be connected with the breakdown of the quantum Hall effect, as proposed previously for alph a-phase salts. The strong two dimensionality leads to an apparent fall of the effective mass together with an overall suppression of the amp litude of the magnetic quantum oscillations at high magnetic fields or very low temperatures. These effects are more pronounced for the Shub nikov-de Haas (SdH) effect but clearly visible also for the de Haas-va n Alphen (dHvA) oscillations. The apparent fall of the effective mass and the deviations of the dHvA signal from the behavior predicted by t he standard Lifshitz-Kosevich theory can quantitatively be explained b y the influence of chemical-potential oscillations on the wave form in a two-dimensional, spin-split Fermi liquid. The much stronger deviati ons from the conventional behavior in the transport data hint to an ad ditional mechanism unique to the SdH effect. [S0163-1829(98)01940-7].