  The first observation of an azimuthal cross--section asymmetry with respect
to the charge of the incoming lepton beam is reported from a study of hard
exclusive electroproduction of real photons. The data have been accumulated by
the HERMES experiment at DESY, in which the HERA 27.6 GeV electron or positron
beam scattered off an unpolarized hydrogen gas target. The observed asymmetry
is attributed to the interference between the Bethe--Heitler process and the
Deeply Virtual Compton Scattering (DVCS) process. The interference term is
sensitive to DVCS amplitudes, which provide the most direct access to
Generalized Parton Distributions.
