  We have realized an integer quantum Hall system with superconducting contacts
by connecting graphene to niobium electrodes. Below their upper critical field
of 4 tesla, an integer quantum Hall effect coexists with superconductivity in
the leads, but with a plateau conductance that is larger than in the normal
state. We ascribe this enhanced quantum Hall plateau conductance to Andreev
processes at the graphene-superconductor interface leading to the formation of
so-called Andreev edge-states. The enhancement depends strongly on the
filling-factor, and is less pronounced on the first plateau, due to the special
nature of the zero energy Landau level in monolayer graphene.
