HIGH-FIELD MAGNETORESISTANCE OF (TMTSF)(2)NO3 - PHASE-TRANSITIONS ANDQUANTUM OSCILLATIONS

Transverse magnetoresistance of the organic conductor (TMTSF)(2)NO3 ha s been measured at ambient pressure, in fields up to 37T and in the te mperature range 2-77K. For field along the lowest conductivity axis (c ), the magnetic field is found to increase the SDW transition tempera ture, in agreement with theoretical predictions for SDW phase with imp erfect nesting. On the other hand, two series of quantum oscillations, with frequency of 63T and 246T respectively, are observed in the 2-10 K range. Both series are connected to the SDW transition but cannot be accounted for by Shubnikov-de Haas model. Anisotropy of these oscilla tions is studied at 4.2K.