  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.
