  A Kondo lattice of strongly interacting f-electrons immersed in a sea of
conduction electrons remains one of the unsolved problems in condensed matter
physics. The problem concerns localized f-electrons at high temperatures which
evolve into hybridized heavy quasi-particles at low temperatures, resulting in
the appearance of a hybridization gap. Here, we unveil the presence of
hybridization gap in Ce2RhIn8 and find the surprising result that the
temperature range at which this gap becomes visible by angle-resolved
photoemission spectroscopy is nearly an order of magnitude lower than the
temperature range where the magnetic scattering becomes larger than the phonon
scattering, as observed in the electrical resistivity measurements. Furthermore
the spectral gap appears at temperature scales nearly an order of magnitude
higher than the coherent temperature. We further show that when replacing In by
Cd to tune the local density of states at the Ce3+ site, there is a strong
reduction of the hybridization strength, which in turn leads to the suppression
of the hybridization gap at low temperatures.
