Clathrate borides have attracted great interest owing to their cagelike boron frameworks with notable properties, including oxidation resistance, exceptional hardness, and superconductivity. Here, we systematically explore the Li-Y-B system across the pressure range of 0–100 GPa through extensive computational structure searches. ${\mathrm{LiYB}}_{12}$ and ${\mathrm{Li}}_2{\mathrm{YB}}_{12}$, forming a unique class of clathrate borides, are predicted to be thermodynamically stable at 5 and 28 GPa, respectively. Both structures comprise ${\mathrm{B}}_{12}$ and ${\mathrm{B}}_{24}$ cages that encapsulate Li and Y atoms, respectively, corresponding to Li-doped ${\mathrm{YB}}_{12}$. Further, electron-phonon coupling computational simulations predict superconducting critical temperatures of $\sim 1\mathrm{K}$ for ${\mathrm{LiYB}}_{12}$ and $\sim 2\mathrm{K}$ for ${\mathrm{Li}}_2{\mathrm{YB}}_{12}$ at 50 GPa, whereas they increase to $\sim 2$ and $\sim 6\mathrm{K}$ at 0 GPa, respectively. In addition, both ${\mathrm{LiYB}}_{12}$ and ${\mathrm{Li}}_2{\mathrm{YB}}_{12}$ are superhard materials with Vickers hardness $\ge 40$ GPa, comparable to that of ${\mathrm{YB}}_{12}$. These findings enrich the chemistry of boron clathrates and suggest a general strategy for designing lightweight superhard superconductors via electron doping of rigid boron-cage frameworks.

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• Hardness
• Superconductivity
• Crystal structures
• BCS theory
• First-principles calculations