Paper by Maxime Barbier

"Herein we show that ${\mathrm{Mo}}_4{\mathrm{Ce}}_4{\mathrm{Al}}_7{C}_3$, a recently discovered nanolamellar compound displaying mixed valence, combines Kondo lattice behavior with ferromagnetism. A sizeable magnetization is carried by $3p$ states of Al as evidenced by a strong x-ray magnetic circular dichroism signal at the $K$ edge of aluminum, whereas no detectable signal was observed at the $K$ edge of carbon and $L_{2,3}$ edges of molybdenum. These results point out that the ferromagnetic behavior originates in the Ce atoms with $4f^1$ electronic configuration lying within the Al planes. The evolution with pressure of the mixed valence of Ce atoms in the Mo-C planes determined via Ce $L_3$ x-ray-absorption spectra along with the magnetoresistance measurements across the ferromagnetic transition unambiguously reveal a Kondo behavior. Angle-resolved photoemission spectroscopy and density functional theory confirm a certain degree of Ce $4f$ electron delocalization. More generally, conduction electrons are not restricted to lie in the MoC planes but are also delocalized in the Al planes."