Spectroscopic evidence of Kondo resonance in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>3</mml:mn><mml:mi>d</mml:mi></mml:mrow></mml:math> van der Waals ferromagnets

Two-dimensional van der Waals (vdW) ferromagnets drive the advancement in spintronic applications and enable the exploration of exotic magnetism in low-dimensional systems. The entanglement of the dual---localized and itinerant---nature of electrons lies at the heart of the correlated electron systems giving rise to exotic ground state properties such as complex magnetism, heavy fermionic behavior, Kondo lattice formation, etc. Through temperature-dependent electronic structure of vdW ferromagnets, ${({\mathrm{Co}}_{x}{\mathrm{Fe}}_{1\ensuremath{-}x})}_{3}{\mathrm{GeTe}}_{2}$, probed using high-resolution photoemission spectroscopy and density functional theory combined with dynamical mean field theory $(\mathrm{DFT}+\mathrm{DMFT})$, we provide direct evidence of the emergence of Kondo resonance peak driven by complex interplay between localized and itinerant electrons. In overall agreement with experimental electronic structure and magnetic properties, $\mathrm{DFT}+\mathrm{DMFT}$ also reveals finite spin band splitting well beyond ${T}_{C}$. Core levels, valence band photoemission spectra together with $\mathrm{DFT}+\mathrm{DMFT}$ spectral functions reveal insignificant change across ${T}_{C}$ indicating non-Stoner magnetism in ${({\mathrm{Co}}_{x}{\mathrm{Fe}}_{1\ensuremath{-}x})}_{3}{\mathrm{GeTe}}_{2}$. Our results provide a way forward to the understanding of complex interplay between electronic structure, exotic magnetism, and heavy fermionic behavior leading to the Kondo scenario in $3d$ vdW ferromagnets.