Quadrupole scattering: Resistivity anisotropy of rare earth impurities in gadolinium

We report measurements of the resistivity of rare-earth impurities in gadolinium in transverse and longitudinal magnetic fields. The resistivity anisotropy turns out to be mainly induced by the interaction of the conduction electrons with the electric quadrupole of the rare-earth impurities. The interpretation of the experimental data allows us an approximate determination of this interaction.