Thermal conductivity of the charge-density-wave systems ${\mathrm{K}}_{0.3}$${\mathrm{MoO}}_3$ and (${\mathrm{TaSe}}_4$${)}_2$I near the Peierls transition

We report on measurements of the thermal conductivity ${\mathrm{\kappa }}_{\mathrm{T}}$ close to the Peierls transition temperature ${\mathrm{T}}_{\mathrm{P}}$ in ${\mathrm{K}}_{0.3}$ ${\mathrm{MoO}}_3$ and (${\mathrm{TaSe}}_4$ ${)}_2$I. In both cases there is an enhancement of ${\mathrm{\kappa }}_{\mathrm{T}}$ that peaks at the transition. Simultaneous measurements of the specific heat suggest that the anomalous behavior is a result of mode occupation rather than changes in electron- or phonon-scattering processes.