Transport properties of very pure copper and silver below 8.5K

Measurements of the thermal and electrical conductivity and thermopower of very pure copper and silver have been made between 1 and 8.5K. The copper samples have been distilled in graphite crucibles to reduce the concentration of magnetic impurities to less than 1 part in 10 9 , which is an order of magnitude improvement over the standard technique of annealing in oxygen. A maximum has been found in the thermopower of silver around 6K and is attributed to phonon drag which is dominated by the scattering of phonons by electrons in the 'neck' region of the Fermi surface. The maximum is suppressed in less pure samples and in samples containing lattice defects. The characteristic thermopower of dislocations in silver is estimated to be between 11 T and 19 T nV K -1 depending on crystal orientation. A similar phonon drag contribution to the thermopower of copper is obscured by a large, negative Kondo term arising from the residual magnetic impurities.