  We report the first observation of an azimuthal asymmetry in the hard
electroproduction of real photons with respect to the charge of the incoming
lepton beam. The asymmetry is attributed to the interference between the
Bethe-Heitler process and the deeply-virtual Compton scattering process, which
gives access to the latter at the amplitude level. This process appears to be
the theoretically cleanest way to access generalized parton distributions. The
data have been accumulated by the HERMES experiment at DESY, scattering the
HERA 27.6 GeV electron/positron beam off an unpolarized hydrogen gas target.
