Thermoelectric studies of KxFe2-ySe2 indicating a weakly correlated superconductor

We report thermal transport properties of a KxFe2-ySe2 superconducting single crystal. A peak anomaly in the thermal conductivity is observed at nearly T-C/2, attributed to phonons. The thermoelectric power above T-c exhibits nearly linear behavior and could be described well by the carrier diffusion mechanism in a wide temperature range. The zero-temperature extrapolated thermoelectric power is smaller than the value in typical strongly correlated superconductors, implying a large normalized Fermi temperature. These findings indicate that KxFe2-ySe2 is a weakly or intermediately correlated superconductor.