Manifestations of Fermi Surface Anisotropy in the Electrical Resistance of Heavy Rare Earths in the Paramagnetic State

In the paramagnetic temperature region for the electrical resistivity it can be shown that where the last ratio refers to projections of the Fermi surface. Critically examining the assumptions involved in these equalities we have evaluated the ratio of the projected areas in the case of dysprosium to be 1.3. This is in good agreement with our careful measurements on dysprosium along both the axes cut from the same monocrystal. Previously reported anomalous values of the slope ratios are discussed. Thus for the heavy rare earths from terbium to lutetium we conclude that it is the anisotropy of the Fermi surface alone which is responsible for the electrical resistivity anisotropy in the paramagnetic temperature region.