SCALING AND THERMAL-CONDUCTIVITY IN UNCONVENTIONAL SUPERCONDUCTORS - THE CASE OF UPT3

We present extensive measurements of the thermal conductivity kappa of a high quality single crystal of the heavy fermion superconductor UPt 3 at low fields and very low temperatures (down to 16 mK). Our kappa(B ,T) data under magnetic fields scale as a function of a single paramet er x = T/T-c root(B-c2/B) yielding to the first observation of the mag netic field-temperature scaling relations recently predicted for a sup erconductor with a line of zeros in the gap. Both the zero field and t he mixed phase measurements of kappa give now a consistent picture reg arding the gap structure of UPt3.