Electric-Field-Dependent Thermopower of NbSe3

We have measured the thermoelectric power of Nb${\mathrm{Se}}_3$ in the temperature range, 10-70 K, where charge-density-wave formation and strongly nonlinear conductivity has been reported. We report the first observation of an electric-field-dependent thermopower. Our results for Nb${\mathrm{Se}}_3$ show that in the presence of an electric field there is an additional negative contribution to the thermopower. Possible mechanisms which may account for this are discussed.