  Two-dimensional band dispersion of (2$\times$2) superstructure with Bi grown
on Ag(111), which has been urged as an ultraflat hexagonal bismuthene, is
investigated using angle-resolved photoemission spectroscopy (ARPES). The
(2$\times$2)-Bi superstructure can be grown on the Ag(111) surface at low
temperatures; it transforms into a surface alloy with a
($\sqrt{3}\times\sqrt{3}$) superstructure at 300 K. ARPES measurements reveal
the consistency with the band structure of ultraflat bismuthene in previous
reports. The band structure of (2$\times$2)-Bi surface remains unchanged with
decreasing Ag layer thickness, indicating the limited penetration of Bi
p-orbitals into the Ag layer.
