Anomalous Thermal Conductivity Of Single Crystal Cu2Te2O5Cl2
  A strong increase of the thermal conductivity is observed at the phase transition (Tc =18.2 K) in Cu2Te2O5Cl2 single crystal. This behavior is compared with that of spin- Peierls system NaV2O5, where similar experimental observation has been found, and the conventional spin-Peierls system CuGeO3, where a modest kink in the thermal conductivity curve has been observed. The strong increase of the thermal conductivity at Tc in Cu2Te2O5Cl2 could be partially attributed to the opening of the energy gap in the magnetic excitation spectrum evident from the magnetic susceptibility measurements. However, the main reason for the anomaly of the thermal conductivity could be explained by a strong spin-lattice coupling in this system, while in NaV2O5 it is a consequence of a charge ordering. 
A. Smontara, A. Bilusic, Z. Jaglicic, J. Dolinsek, H. Berger