Reversal of thermopower oscillations in the mesoscopic Andreev interferometer

We report measurements of phase-periodic thermopower in a diffusive Andreev interferometer. Upon the increase of the dc current applied to the heater electrodes, the amplitude of the thermopower oscillations first increases then goes to zero as one would expect. Surprisingly, the oscillations reappear at yet higher heater currents being inverted compared to low current values. The dependence of the amplitude of the oscillations on temperature strongly correlates with that of the resistance derivative $dR/dT.$