Low temperature resistance anomalies in single crystals of Tb and Dy

Abstract
The authors have investigated the electrical resistivity of Dy and Tb single crystals between 4K and 60 mK. Instead of being temperature independent the resistance decreased by about 1.3% when the temperature was lowered to 60 mK. The effect is isotropic in Dy but seems to be anisotropic in Tb, where for c axis sample the resistance increased again below 0.8K after an initial decrease. The suggested interpretation of the effect is a splitting of impurity levels which can modify the elastic and inelastic scattering of the conduction electrons.