The thermal conductivity of four $\mathrm{Pd}/\mathrm{Ir}$ metal multilayers of total thickness 390 nm with 40, 80, 120, and 200 $\mathrm{Pd}/\mathrm{Ir}$ interfaces are measured at temperatures between 78 and 295 K using time-domain thermoreflectance. The thermal interface conductance $G$ of the $\mathrm{Pd}/\mathrm{Ir}$ interface is derived from the differences in thermal conductivity between the multilayers. A comparison of $G$ to previously reported data for the electronic specific resistance of the $\mathrm{Pd}/\mathrm{Ir}$ interface at 4 K supports the validity of the interfacial form of the Wiedemann-Franz law. The Lorenz number deduced from this comparison is within 10% of the Sommerfeld value at all temperatures, well within the experimental uncertainties of $\approx 20\%$.

• Received 15 March 2012

DOI:https://doi.org/10.1103/PhysRevLett.108.255901