Two-bands effect on the superconducting fluctuating diamagnetism in   MgB&#8322
  The field dependence of the magnetization above the transition temperature Tc in MgB&#8322; is shown to evidence a diamagnetic contribution consistent with superconducting fluctuations reflecting both the &#963; and &#960; bands. In particular, the upturn field Hup in the magnetization curve, related to the incipient effect of the magnetic field in quenching the fluctuating pairs, displays a double structure, in correspondence to two correlation lengths. The experimental findings are satisfactorily described by the extension to the diamagnetism of a recent theory for paraconductivity, in the framework of a zero-dimensional model for the fluctuating superconducting droplets above Tc. 
L.Romano', A.Lascialfari, A.Rigamonti, I.Zucca