Abstract
In $f$-electron heavy fermion systems, a wide variety of fascinating magnetic and electronic properties arise, and they are often thought to be related to a crossover behavior between localized and itinerant regimes for $f$ electrons. Uranium-based compounds with partially occupied $5f$ orbitals provide an ideal platform to elucidate the outstanding issue of the competition between magnetic order and Kondo entanglement. Using angle-resolved photoemission spectroscopy, complemented by density functional theory simulations, we probe the temperature-dependent evolution of the low-energy electronic structure of ${\mathrm{UAs}}_{2}$ and observe two nearly flat bands of different origin in the antiferromagnetic (AFM) state. A nearly flat band which behaves with quasi-two-dimensional character has been observed and contributed to the heavy spectral weight at the \cyrchar\CYRG{} point around ${E}_{\mathrm{F}}$. This flat band reveals typical Kondo hybridization. Another flat band around the $M$ point is closely related to paramagnetic (PM)-AFM phase transition, which opens an energy gap below the transition temperature \ensuremath{\sim}273 K. Our results provide direct spectral demonstration of the electronic structure evolution across the $f\text{\ensuremath{-}}c$ hybridization and PM-AFM transition in ${\mathrm{UAs}}_{2}$.
Published Version
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