Scattering of Conduction Electrons by Magnetic Excitons in a Singlet Ground State System

The electrical resistivity of ${\mathrm{Tb}}_c{\mathrm{Y}}_{1-c}\mathrm{Sb}$ has been measured as a function of temperature and of Tb concentration. The resistivity contribution from scattering of conduction electrons by Tb $4f$ electrons has been calculated in the paramagnetic regime in order to examine the competing effects of the crystal field and the exchange interaction. Excellent agreement with experiment is obtained for the entire range of $c$ with one value for each of the two adjustable parameters, the Fermi momentum, and the electron-ion exchange constant.