Magnetotransport in Cuprates and Related Compounds in High Magnetic Fields:. Evidence for Preformed Bipolarons

By extending the BCS theory to the strong-coupling regime with small bipolarons we explain the common origin of the anomalous upper critical field in high-Tc cuprates, in some organic superconductors, spin ladders and cubic oxides. The bipolaron theory accounts well for the normal state c-axis negative magnetoresistance in high magnetic fileds,¹ normal state diamagnetism,² c-axis tunneling and Andreev reflection,³ angle-resolved photoemission,⁴ normal gaps and stripes⁵ observed in cuprates.