The thermal resistance of tin, indium, and an alloy of tin with 0.134 percent bismuth have been measured as a function of transverse magnetic field strength from zero to values greater than critical at temperatures below their respective superconducting transition temperatures. Measurements have been carried out on tin at several temperatures and with polycrystalline and single-crystal specimens. In all cases a distinct maximum is found in the intermediate state thermal resistance of the pure metals, while no such anomaly is observed in the alloy. The probable origin of this phenomenon is discussed.