  The remarkable Cooper-like pairing phenomenon in the Aharonov-Bohm
interference of a Fabry-Perot interferometer (FPI)$\rm{-}$operating in the
integer quantum Hall regime$\rm{-}$remains baffling. Here, we report the
interference of paired electrons employing 'interface edge modes'. These modes
are born at the interface between the bulk of the FPI and an outer gated region
tuned to a lower filling factor. Such configuration allows toggling the spin
and the orbital of the Landau level (LL) of the edge modes at the interface. We
find that electron pairing occurs only when the two modes (the interfering
outer and the first inner) belong to the same spinless LL.
