Electric Field Dependence of the Magnetoresistance in Nb${\mathrm{Se}}_3$ and ${\mathrm{Fe}}_x\mathrm{Nb}{\mathrm{Se}}_3$

The transverse magnetoresistance of Nb${\mathrm{Se}}_3$ and ${\mathrm{Fe}}_x\mathrm{Nb}{\mathrm{Se}}_3$ ($x<~0.01$) at magnetic fields in the range 100-220 kG shows a strong dependence on applied electric field in the temperature range 20 to 60 K. At 20 K and 206 kG, $\frac{\left[\rho \mathrm{}\right(H)-\rho \mathrm{}(0\left)\right]}{\rho \mathrm{}\left(0\right)\mathrm{}}=4.5\mathrm{}$ at 10 mV/cm and is reduced to 0.9 at 100 mV/cm for pure Nb${\mathrm{Se}}_3$ while the threshold for charge-density-wave sliding motion is ≥ 100 mV/cm. Pinning and unpinning of the charge-density wave with changes of temperature or Fe impurity does not affect the magnetoresistance reduction induced by the electric field.