Anisotropic magnetoresistance of charge-density wave in $o$-TaS$_3$: Anderson localization of soliton

We report magnetoresistance of charge-density wave (CDW) in $o$-TaS$_3$ whiskers. Anisotropic negative magnetoresistance is found in the nonlinear regime of current-voltage characteristics. The angle dependence of the magnetoresistance exhibits two-fold symmetry, suggesting that two-dimensionality plays an important role for the electric transport phenomenon. This result can be understood qualitatively in terms of Anderson localization of a CDW soliton. From the differences of the offset angle of the magnetoresistance among the samples, it is more plausible to attribute the results to a global property of each sample, rather than symmetry of the crystal structure. We deduce the CDW solitons are randomly distributed in a plane. Our findings are consistent with the previous studies of Aharonov-Bohm oscillations in CDW ring, and also provides a possible reason the oscillations were able to be observed in the experiments.