Activated and quantum creep of the charge-density waves in magnetic field in {\it o}-TaS${}_3$

We demonstrate that magnetoresistance of creeping charge-density waves in the quasi-one dimensional conductor {\it o}-TaS${}_3$ changes its character from a negative parabolic at $T\gtrsim 10$ K where it obeys $1\mathrm{/}{T}^2$ law to a weakly temperature dependent negative nearly linear one at lower temperatures. The dominant contribution into the negative parabolic magnetoresistance comes from magnetic field induced splitting of the CDW order parameter. The linear magnetoresistance arises due to CDW quantum interference similar to the scenario of negative linear magnetoresistance in single-electron systems.