Thermal conductivity of the spin-Peierls compound ${\mathrm{CuGeO}}_3$

The thermal conductivity $\kappa$ of the spin-Peierls (SP) compound ${\mathrm{CuGeO}}_3$ was measured in magnetic fields up to 16 T. Above the SP transition, the heat transport due to spin excitations causes a peak at $\sim 22$ K, while below the transition the spin excitations rapidly diminish and the heat transport is dominated by phonons; however, the main scattering process of the phonons is with spin excitations, which demonstrates itself in an unusual peak in $\kappa$ at $\sim 5.5$ K. This low-temperature peak is strongly suppressed with magnetic fields in excess of 12.5 T.