  The periodical dependencies in magnetic field of the asymmetry of the
current-voltage curves of asymmetric aluminum loop are investigated
experimentally at different temperatures below the transition into the
superconducting state T < Tc. The obtained periodical dependencies of the
critical current on magnetic field allow to explain the quantum oscillations of
the dc voltage as consequence of the rectification of the external ac current
and to calculate the persistent current at different values of magnetic flux
inside the loop and temperatures.
