  Using angle-resolved photoemission spectroscopy (ARPES) and low-energy
electron diffraction (LEED), together with density-functional theory (DFT)
calculation, we report the formation of charge density wave (CDW) and its
interplay with the Kondo effect and topological states in CeSbTe. The observed
Fermi surface (FS) exhibits parallel segments that can be well connected by the
observed CDW ordering vector, indicating that the CDW order is driven by the
electron-phonon coupling (EPC) as a result of the nested FS. The CDW gap is
large (~0.3 eV) and momentum-dependent, which naturally explains the robust CDW
order up to high temperatures. The gap opening leads to a reduced density of
states (DOS) near the Fermi level (EF), which correspondingly suppresses the
many-body Kondo effect, leading to very localized 4f electrons at 20 K and
above. The topological Dirac cone at the X point is found to remain gapless
inside the CDW phase. Our results provide evidence for the competition between
CDW and the Kondo effect in a Kondo lattice system. The robust CDW order in
CeSbTe and related compounds provide an opportunity to search for the
long-sought-after axionic insulator.
