Failure of the empirical OCT law in the Bi2Sr2CuO6+d compound
  We have studied the evolution of the thermoelectric power S(T) with oxygen doping of single-layered Bi2Sr2CuO6+d thin films and ceramics in the overall superconducting (Tc, S290K) phase diagram. While the universal relation between the room-temperature thermopower S290K and the critical temperature is found to hold in the strongly overdoped region (d>0.14), a strong violation is observed in the underdoped part of the phase diagram. The observed behaviour is compared with other cuprates and the different scenarios are discussed. 
Z. Konstantinovic, G. Le Bras, A. Forget, D. Colson, F. Jean, G.   Collin, Z.Z. Li, H. Raffy, C. Ayache