Verification of Wiedemann–Franz Law in Silver with Moderate Residual Resistivity Ratio

Electrical and thermal transport were studied in a vacuum-annealed polycrystalline silver wire with residual resistivity ratio 200 – 400, in the temperature range 0.1-1.2 K and in magnetic fields up to 5 T. Both at zero field and at 5 T the wire exhibits the Wiedemann–Franz law with the fundamental Lorenz number, contrary to an earlier report (Gloos et al., in Cryogenics 30:14–18, 1990). Our result demonstrates that silver is an excellent material for thermal links in ultra-low-temperature experiments operating at high magnetic fields.