Crystal structure stability and electronic properties of layered nickelate La${}_4$Ni${}_3$O${}_{10}$

We investigate the crystal structure and the electronic properties of the trilayer nickelate La${}_4$Ni${}_3$O${}_{10}$ by means of quantum mechanical calculations in the framework of the density functional theory. We find that, at low temperature, La${}_4$Ni${}_3$O${}_{10}$ undergoes a hitherto unreported structural phase transition and transforms to a new monoclinic $P{2}_1\mathrm{/}a$ phase. This phase exhibits electronic properties in agreement with recent angle-resolved photoemission spectroscopy data reported in H.\ Li \emph{et al}., Nat.\ Commun.\ $\mathbf{\text{8}}$, 704 (2017) and should be considered in models focused on explaining the observed $\sim$140,K metal-to-metal phase transition.