Signature of weakly coupled f electrons and conduction electrons in magnetic Weyl semimetal candidates PrAlSi and SmAlSi

Magnetic topological materials are a class of compounds with the underlying interplay of nontrivial band topology and magnetic spin configuration. Extensive interest has been aroused due to their application potential involved with an array of exotic quantum states. With angle-resolved photoemission spectroscopy and first-principles calculations, here we study the electronic properties of two magnetic Weyl semimetal candidates, PrAlSi and SmAlSi. Though the two compounds harbor distinct magnetic ground states (ferromagnetic and antiferromagnetic for PrAlSi and SmAlSi, respectively) and $4f$ shell fillings, we find that they share a quite analogous low-energy band structure. By measurements across the magnetic transitions, we further reveal that there is no evident evolution of the band structure in both compounds and the experimental spectra can be well reproduced by the nonmagnetic calculations, together suggesting a negligible effect of the magnetism on their electronic structures and a possibly weak coupling between the localized $4f$ electrons and the itinerant conduction electrons. Our results offer essential insights into the interactions between magnetism, electron correlations, and topological orders in the $R\mathrm{Al}X$ ($R$ = light rare earth and $X$ = Si or Ge) family.