Low-temperature resistivity and thermoelectric ratio of copper and gold

The resistivity ρ and thermoelectric ratio G have been measured between 0.04 and {~}7 K for "pure" polycrystalline samples of copper and gold, in a dilution refrigerator with a superconducting quantum-interference device null detector system. The measurements confirm that these metals, like silver, show a ρ-ρ₀∝T⁴ temperature dependence over a substantial temperature range. For the best copper sample a ρ-ρ₀∝T2.03 temperature dependence below 2 K is strong evidence for electron-electron scattering.