Observation of commensurability oscillations of thermopower in an antidot lattice

Commensurability oscillations of thermopower in a square antidot lattice are observed. The oscillations are attributed to the geometrical resonances of the classical electron motion in a magnetic field and are much more pronounced than the corresponding magnetoresistance oscillations. The off-diagonal component of the thermopower tensor (the Nernst-Ettingshausen effect) changes sign at resonances. Additional measurements of magnetoresistance verify the correctness of the method used for thermopower measurements and provide information on the temperature distribution in the sample.