C-axis negative magnetoresistance and upper critical field of   Bi2Sr2CaCu2O8
  The out-of-plane resistance and the resistive upper critical field of BSCCO-2212 single crystals with Tc=91-93 K have been measured in magnetic fields up to 50 T over a wide temperature range. The results are characterised by a positive linear magnetoresistance in the superconducting state and a negative linear magnetoresistance in the normal state. The zero field normal state c-axis resistance, the negative linear normal state magnetoresistance, and the divergent upper critical field Hc2(T)are explained in the framework of the bipolaron theory of superconductivity. 
V.N. Zavaritsky (1 and 2), M. Springford (2), A.S. Alexandrov (3) ((1)   H.H. Wills Physics Laboratory, University of Bristo...