  Exposure of highly oriented pyrolytic graphite to bromine vapor gives rise to
in-plane charge conductivities which increase monotonically with intercalation
time toward values (for ~6 at% Br) that are significantly higher than Cu at
temperatures down to 5 K. Magnetotransport, optical reflectivity and magnetic
susceptibility measurements confirm that the Br dopes the graphene sheets with
holes while simultaneously increasing the interplanar separation. The increase
of mobility (~ 5E4 cm^2/Vs at T=300 K) and resistance anisotropy together with
the reduced diamagnetic susceptibility of the intercalated samples suggests
that the observed supermetallic conductivity derives from a parallel
combination of weakly-coupled hole-doped graphene sheets.
