In-plane Hall-effect anisotropy in the organic superconductor kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br

Anisotropy of the Hall effect within the highly conducting plane has been m easured in the organic superconductor kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br. An isotropy and magnetic field dependence nonlinearity in the Hall resistivity are found above approximately 30 K. This behavior is shown to originate fr om an electron sheet of the Fermi surface. The temperature at which anisotr opy and nonlinearity appear correlates with the temperature at which resist ivity is at its maximum. The Hall effect behavior at temperatures below abo ut 30 It corresponds to the predictions of the semiclassical weak-field mod el for a two-dimensional metal. A comparison of the Hall constant predicted by the calculated band structure within this model with the experimentally determined value revealed a large discrepancy. This is discussed within th e framework of a reconstruction of the Fermi surface, as recently proposed by Weiss et al. on the basis of Shubnikov-de Haas effect studies under pres sure. [S0163-1829(99)12233-1].