  We consider the production of a lepton-antilepton pair by real photons off a
hadronic target. The interference of one and two photon exchange amplitudes
leads to a charge asymmetry term that may be calculated explicitly in the
large-t limit in terms of hadronic distribution amplitudes. A rather compact
expression emerges for the leading order asymmetry at fixed angle in the
centre-of-mass of the lepton pair. The magnitude appears sizeable and is
approximately independent of the pair mass in the asymptotic limit.
