Thermopower of a multiprobe ballistic conductor

The thermopower of a multiprobe ballistic conductor in the form of caterpillarlike Sinai billiard is experimentally investigated. The magnetic-field dependence of both longitudinal thermopower and Nernst-Ettingshausen effect exhibits commensurability oscillations, which are more pronounced than the corresponding oscillations in the magnetoresistance. Results of computer calculations based on the generalized Landauer-Buttiker approach are in agreement with experiment. The observed features in the thermopower originate from drastic difference between the transmission coefficients of quasielectrons (above the Fermi level) and quasiholes (below the Fermi level) in the vicinity of geometrical resonances.