- Hepting, M
- Li, D
- Jia, CJ
- Lu, H
- Paris, E
- Tseng, Y
- Feng, X
- Osada, M
- Been, E
- Hikita, Y
- Chuang, Y-D
- Hussain, Z
- Zhou, KJ
- Nag, A
- Garcia-Fernandez, M
- Rossi, M
- Huang, HY
- Huang, DJ
- Shen, ZX
- Schmitt, T
- Hwang, HY
- Moritz, B
- Zaanen, J
- Devereaux, TP
- Lee, WS
- et al.
The search continues for nickel oxide-based materials with electronic properties similar to cuprate high-temperature superconductors1-10. The recent discovery of superconductivity in the doped infinite-layer nickelate NdNiO2 (refs. 11,12) has strengthened these efforts. Here, we use X-ray spectroscopy and density functional theory to show that the electronic structure of LaNiO2 and NdNiO2, while similar to the cuprates, includes significant distinctions. Unlike cuprates, the rare-earth spacer layer in the infinite-layer nickelate supports a weakly interacting three-dimensional 5d metallic state, which hybridizes with a quasi-two-dimensional, strongly correlated state with [Formula: see text] symmetry in the NiO2 layers. Thus, the infinite-layer nickelate can be regarded as a sibling of the rare-earth intermetallics13-15, which are well known for heavy fermion behaviour, where the NiO2 correlated layers play an analogous role to the 4f states in rare-earth heavy fermion compounds. This Kondo- or Anderson-lattice-like 'oxide-intermetallic' replaces the Mott insulator as the reference state from which superconductivity emerges upon doping.