Cubic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>BeB</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>: A metastable <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>p</mml:mi></mml:math>-type conductive

Boron forms a wide variety of compounds with alkaline earth elements because of its unique bonding characteristics. Among these, binary compounds of Be and B display particularly rich structural diversity, attributed to the small atomic size of Be. Cubic ${\mathrm{BeB}}_{2}$ is a particularly interesting phase, in which Be donates electrons to stabilize a diamond-like boron network under high pressure. In this work, we employ ab initio methods to conduct a detailed investigation of cubic ${\mathrm{BeB}}_{2}$ and its functional properties. We show that this metastable phase is dynamically stable under ambient conditions, and its lattice match to existing substrate materials suggests possible epitaxial stabilization via thin-film growth routes. Through a comprehensive characterization of its electronic, transport, and superconductivity properties, we demonstrate that cubic ${\mathrm{BeB}}_{2}$ exhibits high hole concentrations and high hole mobility, making it a potential candidate for efficient $p$-type transport. In addition, cubic ${\mathrm{BeB}}_{2}$ is found to exhibit low-temperature superconductivity at degenerate doping levels, similar to several other doped covalent semiconductors such as diamond, Si, and SiC.