Fermi-level flat band in a kagome magnet

The band structure in a kagome lattice can naturally exhibit flat band, Dirac cones, and van Hove singularity, enabling rich interplays between correlation and topology. However, the flat band is rarely detected just at the Fermi level in kagome materials, which would be crucial to realize emergent flat band physics. Here, combining angle-resolved photoemission spectroscopy, transport measurements and first-principles calculation, we observe a striking Fermi-level flat band in paramagnetic YCr6Ge6 as a typical signature of electronic kagome lattice. We explicitly unveil that orbital character plays an essential role to realize electronic kagome lattice in crystals with transition-metal kagome layers. We further engineer this material with magnetic rare earth elements to break the time-reversal symmetry of the Fermi-level kagome flat band. Our work establishes a Fermi-level flat band in a kagome magnet as an exciting quantum platform.