  The Kondo lattice physics, describing the hybridization of localized spin
matrix with dispersive conduction electrons, breeds numerous discoveries in the
realm of strongly correlated quantum matter. Generally observed in lanthanide
and actinide compounds, increasing attention has been directed towards
alternative pathways for achieving flat band structures, such as Morie
superlattices and Kagome metals. However, fine control of Kondo interaction
outside of heterostructures remains elusive. Here we report the discovery of a
van der Waals (vdW) kagome antiferromagnet CsCr6Sb6. Angle-resolved
photoemission spectra and theoretical analysis show clear flat bands,
consisting of half-filled 3dxz and 3dyz orbitals of Cr, situated 50 meV below
the Fermi level. Importantly, we observe the emergence of anomalous Hall effect
with remarkable tunability by simple reduction the sample thickness. The
effective control of kondo interaction in CsCr6Sb6 render it an ideal platform
for exploring unpresented phenomena using the vast toolkit of vdW structures.
