  Intercalation is an established technique for tailoring the electronic
structure of epitaxial graphene. Moreover, it enables the synthesis of
otherwise unstable two-dimensional (2D) layers of elements with unique physical
properties compared to their bulk versions due to interfacial quantum
confinement. In this work, we present uniformly Pb-intercalated
quasi-freestanding monolayer graphene on SiC, which turns out to be essentially
charge neutral with an unprecedented $p$-type carrier density of only
$(5.5\pm2.5)\times10^9$ cm$^{-2}$. Probing the low-energy electronic structure
throughout the entire first surface Brillouin zone by means of momentum
microscopy, we clearly discern additional bands related to metallic 2D-Pb at
the interface. Low-energy electron diffraction further reveals a $10\times10$
Moir\'e superperiodicity relative to graphene, counterparts of which cannot be
directly identified in the available band structure data. Our experiments
demonstrate 2D interlayer confinement and associated band structure formation
of a heavy-element superconductor, paving the way towards strong spin-orbit
coupling effects or even 2D superconductivity at the graphene/SiC interface.
