Violation of Kohler's rule in the magnetoresistance near the lower charge-density-wave instability in NbSe3

This paper reports the measurements of resistance (R) and magnetoresistance of NbSe3 near the critical pressure (P-c = 7.5 kbar), where the lower charge-density-wave (CDW) phase is on the verge of destruction. For P = 7.6 kbar, the temperature dependence of dR/dT exhibits a weak anomaly at T* 15 K and the superconducting transition is observed at T-c = 2.8 K. From the observation of a large magnetoresistance due to an imperfect nesting of Fermi surface, we show that the weak anomaly is closely related to the lower CDW phase. Moreover, an excess conductance and violation of Kohler's rule are found below similar to T*. The origins of the excess conductance and the violation of Kohler's rule are discussed in terms of charge fluctuation associated with the lower CDW state.