  We present high-resolution angle-resolved photoemission spectroscopy study in
conjunction with first principles calculations to investigate how the
interaction of electrons with phonons in graphene is modified by the presence
of Yb. We find that the transferred charges from Yb to the graphene layer
hybridize with the graphene $\pi$ bands, leading to a strong enhancement of the
electron-phonon interaction. Specifically, the electron-phonon coupling
constant is increased by as much as a factor of 10 upon the introduction of Yb
with respect to as grown graphene ($\leq$0.05). The observed coupling constant
constitutes the highest value ever measured for graphene and suggests that the
hybridization between graphene and the adatoms might be a critical parameter in
realizing superconducting graphene.
