Field enhancement of the diamagnetic onset temperature in a YBa2Cu3O6.45 single crystal

Abstract The diamagnetic response χ(T), measured on a YBa 2 Cu 3 O 6.45 single crystal for H a  c shows an unusual field induced splitting of the superconducting transition into two sharp diamagnetic transitions at T=T c1 and T c2 (T c1 >T c2 ). An applied field H a = 250 Oe enhances by 27 K the value of T c1 with respect to the superconducting transition temperature T co = 47 K measured in the limit H a → 0.