Scaling and Thermal Conductivity in Unconventional Superconductors: The Case ofUPt3

We present extensive measurements of the thermal conductivity κ of a high quality single crystal of the heavy fermion superconductor ${\mathrm{UPt}}_3$ at low fields and very low temperatures (down to $16\mathrm{mK}$). Our $\kappa (B,T)$ data under magnetic fields scale as a function of a single parameter ${x=T/T}_c\sqrt{B_{c2\mathrm{}}/B}$ yielding to the first observation of the magnetic field-temperature scaling relations recently predicted for a superconductor with a line of zeros in the gap. Both the zero field and the mixed phase measurements of κ give now a consistent picture regarding the gap structure of ${\mathrm{UPt}}_3$.