Fine Structure of In-Plane Angular Effect of Magnetoresistance of (DMET)2I3

The magnetoresistance of a quasi-one-dimensional (Q1D) organic superconductor, (DMET) 2 I 3 , where DMET is dimethyl(ethylenedithio)diselenadithiafulvalene, was measured up to 30 T at 1.5 K. An electrical current was applied perpendicular to the conducting a b plane and a magnetic field is rotated in the a b plane. An anomalous hump of the magnetoresistance reported previously was observed at 7 T between -15° and 15° from the most conducting b -axis. It was found that the hump has a fine structure at higher magnetic fields with two additional sharp local minima at about ±3°. Partial disappearance of the Q1D Fermi surface at a critical angle, where a kind of quantum limit is realized, is proposed to interpret the fine structure.