As sharing similar layered structure and close electron configuration with the high-Tc cuprate superconductors, various series of nickel oxides have naturally become potential candidates for cuprate analogues. A previous study found a rare metallic state lying in the trilayer nickelate Pr₄Ni₃O₈ (Pr438) with a quasi-2D lattice structure, which together with similar d-electron counting to the overly hole-doped cuprates and strong orbital polarization near the Fermi energy has drawn more attention to this compound^[1]. Here we present a more direct and detailed study of the electronic structure of Pr438, with a combination of the Angle-resolved photoemission spectroscopy and Density-functional-theory calculations. Our spectroscopy data shows a non-gapped Fermi surface resembling the heavily hole-doped cuprates residing in the Fermi-liquid regime, bearing both electron- and hole-pockets, as has been corroborated by DFT calculations. These combine the predominant d_x2-y2 feature and strong hybridization between the Ni-3d and O-2p states, rendering Pr438 an extraordinary analogue to cuprates, making it a promising host for superconductivity.

[1]Junjie Zhang, A.S.Botana, et al. Nat. Phys. 13, 864–869 (2017)