  We utilized high-resolution resonant angle-resolved photoemission
spectroscopy (ARPES) to study the band structure and hybridization effect of
the heavy-fermion compound Ce2IrIn8. We observe a nearly flat band at the
binding energy of 7 meV below the coherent temperature Tcoh ~ 40 K, which
characterizes the electrical resistance maximum indicating the onset
temperature of hybridization. However, the Fermi vector kF and the Fermi
surface (FS) volume have little change around Tcoh, challenging the widely
believed evolution from a high-temperature small FS to a low-temperature large
FS. Our experimental results of the band structure fit well with the density
functional theory plus dynamic mean-field theory (DFT+DMFT) calculations.
