Correspondence: The fermiology and electron dynamics of trilayer nickelate La$_4$Ni$_3$O$_{10}$

In their paper, Li et al. [Nat. Commun. 8, 704 (2017)], analyse the Fermi surface of the trilayer nickelate La$_4$Ni$_3$O$_{10}$ using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) band structure calculations. The study describes the similarities and differences between the low-energy electronic structure of layered cuprates and nickelates; nonetheless, we find critical inconsistencies between the ARPES and DFT calculations based on a correctly simulated orthorhombic $Bmab$ phase of La$_4$Ni$_3$O$_{10}$, which refute the main claim that "La$_4$Ni$_3$O$_{10}$ has no pseudogap in the $d_{x^2-y^2}$ band, while it has an extra band of principally $d_{3z^2-r^2}$ orbital character, which presents a low temperature energy gap." We show that orthorhombic La$_4$Ni$_3$O$_{10}$ exhibits no pseudogap and that reconciliation between the ARPES data reported by Li et al. and the DFT band structure requires that La$_4$Ni$_3$O$_{10}$ is monoclinic at low-temperature, indicating it likely undergoes a displacive transition. Only the monoclinic phase exhibits the observed pseudogap.