Anomalies in the thermal conductivity and thermopower in CoCl2-intercalated graphite at the magnetic phase transition

The thermal conductivity and thermoelectric power (TEP) of a stage-3 graphite-Co${\mathrm{Cl}}_2$ intercalation compound have been measured between 4 and 300 K. In the temperature region $4<T<\mathrm{}13\mathrm{}$ K there appears a contribution to the thermal conductivity in addition to the one that is linear in $T$ and associated with free carriers. This additional contribution reaches a maximum near 9.5 K. At that temperature the curve of TEP vs $T$ displays a sharp break in slope. The temperature of these anomalies is consistent with the temperature of a magnetic phase transition deduced from magnetic-susceptibility and heat-capacity measurements.