Abstract
The thermopower of a quantum dot, defined in the two-dimensional electron gas in a GaAs-AlxGa1-xAs heterostructure, is investigated using a current heating technique. At lattice temperatures kBT much smaller than the charging energy e2/C, and at small heating currents, sawtoohlike thermopower oscillations are observed as a function of gate voltage, in agreement with a recent theory. In addition, a remarkable sign reversal of the amplitude of the thermopower oscillations is found in the non-linear regime at large heating currents.