Thermal Conductivity of Pure ${\mathrm{He}}^3$ and of Dilute Solutions of ${\mathrm{He}}^3$ in ${\mathrm{He}}^4$ at Low Temperatures

The thermal conductivity $\kappa$ of pure ${\mathrm{He}}^3$ and of two dilute solutions of ${\mathrm{He}}^3$ in ${\mathrm{He}}^4$ has been measured from 30 down to 5 mdeg K or below. For pure ${\mathrm{He}}^3$, $\kappa T$ increases with increasing temperature. For the dilute solutions at low enough temperatures, $\kappa$ is consistent with the $T^{-1\mathrm{}}$ temperature dependence of a normal Fermi liquid, but the magnitudes of $\kappa T$ do not agree with values computed from an effective potential based on spin-diffusion coefficient measurements.