  We report on a strongly coupled bilayer graphene (BLG) - \bise\ device with a
junction resistance of less than 1.5 k$\Omega\mu$m$^2$. This device exhibits
unique behavior at the interface, which cannot be attributed to either material
in absence of the other. We observe quantum oscillations in the
magnetoresistance of the junction, indicating the presence of well-resolved
Landau levels due to hole carriers of unknown origin with a very large Fermi
surface. These carriers, found only at the interface, could conceivably arise
due to significant hole doping of the bilayer graphene with charge transfer on
the order of 2$\times$10$^{13}$ cm$^{-2}$, or due to twist angle dependent
mini-band transport.
