  Nonlinear transport coefficients do not obey, in general, reciprocity
relations. We here discuss the magnetic-field asymmetries that arise in
thermoelectric and heat transport of mesoscopic systems. Based on a scattering
theory of weakly nonlinear transport, we analyze the leading-order symmetry
parameters in terms of the screening potential response to either voltage or
temperature shifts. We apply our general results to a quantum Hall antidot
system. Interestingly, we find that certain symmetry parameters show a
dependence on the measurement configuration.
