  Our recently reported spin and angular resolved photoemission (SARPES)
results on an epitaxial graphene monolayer on SiC(0001) suggested the presence
of a large Rashba-type spin splitting of \Delta k=(0.030+-0.005)1/A [1].
Although this value was orders of magnitude larger than predicted
theoretically, it could be reconciled with the line width found in conventional
spin-integrated high resolution angular resolved photoemission spectroscopy
(ARPES) data. Here we present novel measurements for a hydrogen intercalated
quasi free-standing graphene monolayer on SiC(0001) that reveal a spin
polarization signal that - when interpreted in terms of the Rashba-Bychkov
effect [2,3] - corresponds to a spin splitting of \Delta k=(0.024+-0.005)1/A.
This splitting is significantly larger than the half width at half maximum of
spin-integrated high resolution ARPES measurements which is a strong indication
that the measured polarization signal does not originate from a Rashba-type
spin splitting of the graphene pi-bands as we suggested in our previous report
[1].
