High-pressure chemistry is known to inspire the creation of unexpected new classes of compounds with exceptional properties. Here, we employ the laser-heated diamond anvil cell technique for synthesis of a Dirac material ${\mathrm{BeN}}_4$. A triclinic phase of beryllium tetranitride $\mathrm{tr}\text{−}{\mathrm{BeN}}_4$ was synthesized from elements at $\sim 85\mathrm{GPa}$. Upon decompression to ambient conditions, it transforms into a compound with atomic-thick ${\mathrm{BeN}}_4$ layers interconnected via weak van der Waals bonds and consisting of polyacetylene-like nitrogen chains with conjugated $\pi$ systems and Be atoms in square-planar coordination. Theoretical calculations for a single ${\mathrm{BeN}}_4$ layer show that its electronic lattice is described by a slightly distorted honeycomb structure reminiscent of the graphene lattice and the presence of Dirac points in the electronic band structure at the Fermi level. The ${\mathrm{BeN}}_4$ layer, i.e., beryllonitrene, represents a qualitatively new class of 2D materials that can be built of a metal atom and polymeric nitrogen chains and host anisotropic Dirac fermions.

Three oxygen-free pentazolate salts Na₂N₅, NaN₅and NaN₅·N₂were synthesized from sodium azide NaN₃and molecular nitrogen N₂at 50 GPa.

The sulfur-hydrogen system is the first one in which superconductivity at temperatures over 200 K has been reported, albeit at high pressure. The particular phases causing the measured $T_c$ and their structures are not yet firmly identified. Here, synchrotron single-crystal x-ray diffraction studies of S-H samples were performed up to 150 GPa and revealed two previously unobserved and unpredicted sulfur-hydrogen phases—${\mathrm{H}}_{6\pm x}{\mathrm{S}}_5$ with $x\sim 0.4$, and ${\mathrm{H}}_{2.85\pm y}{\mathrm{S}}_2$ with $y\sim 0.35$. The crystallographic data obtained in this work, both for the new phases and for the previously identified ${\mathrm{H}}_3\mathrm{S}$ polymorphs, provide an unambiguous experimental proof of the chemical richness of the S-H system and the structural diversity of compounds forming at high pressures and high temperatures. Our results have profound implications for the interpretation of the resistance, superconductivity, and other physical properties measurements on the complex S-H system.