Superconducting states onsetting at moderately high temperatures have been observed in epitaxially stabilized RENiO₂-based thin films. However, recently, it has also been reported that superconductivity at high temperatures is observed in bulk La₃Ni₂O_7-δ at high pressure, opening further possibilities for study. Here we report the reduction profile of La₃Ni₂O₇ in a stream of 5% H₂/Ar gas and the isolation of the metastable intermediate phase La₃Ni₂O_6.45, which is based on Ni²⁺. Although this reduced phase does not superconduct at ambient or high pressures, it offers insights into the Ni-327 system and encourages future study of nickelates as a function of oxygen content.

Pyroxenes (AMX₂O₆) consisting of infinite one-dimensional edge-sharing MO₆chains and bridging XO₄tetrahedra are fertile ground for finding quantum materials. Thus, here, we have studied calcium cobalt germanate (CaCoGe₂O₆) and calcium cobalt silicate (CaCoSi₂O₆) crystals in depth. Heat capacity data show that the spins in both compounds are dominantly Ising-like, even after being manipulated by high magnetic fields. On cooling below the Néel temperatures, a sharp field–induced transition in magnetization is observed for CaCoGe₂O₆, while multiple magnetization plateaus beneath the full saturation moment are spotted for CaCoSi₂O₆. Our analysis shows that these contrasting behaviors potentially arise from the different electron configurations of germanium and silicon, in which the 3d orbitals are filled in the former but empty in the latter, enabling electron hopping. Thus, silicate tetrahedra can aid the interchain superexchange pathway between cobalt(II) ion centers, while germanate ones tend to block it during magnetization.

In continuation of research into RuCl₃ and RuBr₃ as potential quantum spin liquids, a phase with unique magnetic order characterised by long-range quantum entanglement and fractionalised excitations, the compound RuI₃ has been recently synthesised. Here, we show RuI₃ is a moderately correlated metal with two bands crossing the Fermi level, implying the absence of any quantum spin liquids phase. We find that the Fermi surface as measured or calculated for a 2D (k_x, k_y) slice at any k_z lacks mirror symmetry, i.e. is pseudochiral. We link this phenomenon to the ABC stacking in the R $$\bar{3}$$3 ¯ space group of α-RuI₃, which is achiral but lacks any mirror or glide symmetries. We further provide a formal framework for understanding when such a pseudochiral electronic structure may be observed.