HYSTERETIC MAGNETIC STATE IN THE ORGANIC TAU-PHASE CONDUCTORS

The tau-phase conductors are known to exhibit resistance upturn and ne gative magnetoresistance below T-min similar to 50 K. Well below T-min , at least in the range of about 1 to several K, a large hysteresis in the field sweep as well as angle sweep is observed in the configurati on of current, I-parallel to or I-perpendicular to, and magnetic field , with B-parallel to or B-perpendicular to, where parallel to and perp endicular to refer to the two-dimensional a-b plane. Furthermore, with I-perpendicular to and B-parallel to, symmetry of the angular depende nce of magnetoresistance varied between four-fold and two-fold dependi ng on the region of T and B. Two-fold symmetry is hard to understand f rom the symmetry of the crystal and the relevant Fermi surface. Althou gh many of the phenomena are unexplained, we believe that we have obse rved a new type of electronic property. (C) 1998 Elsevier Science S.A. All rights reserved.