  Topological kagome systems have been a topic of great interest in condensed
matter physics due totheir unique electronic properties. The vanadium-based
kagome materials are particularly intrigu-ing since they exhibit exotic
phenomena such as charge density wave (CDW) and
unconventionalsuperconductivity. The origin of these electronic instabilities
is not fully understood, and the re-cent discovery of a charge density wave in
ScV6Sn6provides a new avenue for investigation. In thiswork, we investigate the
electronic structure of the novel kagome metal ScV6Sn6using angle
resolvedphotoemission spectroscopy (ARPES), scanning tunneling microscopy
(STM), and first-principlesdensity functional theory calculations. Our analysis
reveals for the first time the temperature-dependent band changes of ScV6Sn6and
identifies a new band that exhibits a strong signatureof a structure with CDW
below the critical temperature. Further analysis revealed that this newband is
due to the surface kagome layer of the CDW structure. In addition, a Lifshitz
transition isidentified in the ARPES spectra that is related to the saddle
point moving across the Fermi levelat the critical temperature for the CDW
formation. This result shows the CDW behavior may alsobe related to nesting of
the saddle point, similar to related materials. However, no energy gap is
observed at the Fermi level and thus the CDW is not a typical Fermi surface
nesting scenario. These results provide new insights into the underlying
physics of the CDW in the kagome materials and could have implications for the
development of materials with new functionality.
