Abstract
The thermal conductivity and electrical resistivity of Dy, Er, and Lu single crystals have been measured from 5 to 300°K. The Lorenz functions were calculated from the experimental results, and they exceeded the value expected for pure electron heat conduction. This indicated that phonons and/or magnons must contribute significantly to the heat conduction. At high temperatures the thermal conductivity was separated into suggested electron and phonon contributions. The magnetic transitions in Dy and Er produced an anisotropic effect on the thermal conductivity which is interpreted on the basis of magnetic superzones. A high-temperature anisotropy is explained by the anisotropic shape of the Fermi surface.