Thermopower and anomalous heat transport

The thermopower and thermal conductivity of (Formula presented) have been studied as a function of temperature and magnetic field. Huge changes of the thermopower of about one order of magnitude have been observed in the vicinity of the metal-insulator (Formula presented) transition. The measured relative change of the thermopower was found to be proportional to that of the resistivity. Furthermore, a magnetic-field-dependent anomaly of the thermal conductivity was found in the vicinity of the (Formula presented) transition that cannot be explained by a variation of the electric conductivity alone but requires a magnetic-field-dependent lattice contribution. This signals the importance of the lattice dynamics for understanding the details of the (Formula presented) transition.