Intermetallic nuclear fuel materials, in particular the uranium alloyed with Zr, Mo, Nb, Ti, offer superior swelling, fabrication, and fuel-cladding chemical reaction properties, among others. However, similar to pure $\alpha$-uranium, the alloyed uranium compositions exhibit susceptibility to a charge-density-wave (CDW) instability at low temperatures, which has rarely been investigated in detail. Here, we unequivocally experimentally identify CDW instability in ${\gamma }^{\prime }\text{−}{\mathrm{U}}_2\mathrm{Mo}$ using diffraction and heat capacity measurements on hitherto unreported single-phase ${\gamma }^{\prime }\text{−}{\mathrm{U}}_2\mathrm{Mo}$. We find that ${\gamma }^{\prime }\text{−}{\mathrm{U}}_2\mathrm{Mo}$ undergoes phase transformation from ordered intermetallic tetragonal ($I4/mmm$) phase to monoclinic symmetry ($C2/c$) below $T_{\mathrm{CDW}}\sim 200\mathrm{K}$, which remains stable at least up to 10 K. Ab initio molecular dynamics simulations confirm the CDW instability, and the CDW phase is determined. A detailed analysis of electronic structures and the real and imaginary parts of electronic susceptibility suggests the role of Fermi-surface nesting and hidden nesting leading to phonon instabilities that induce the CDW distortion. Our results emphasize the need for careful investigation of low-temperature CDW instability in other single-phase intermetallic nuclear fuels.

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• Charge density waves
• First-principles calculations
• Lattice dynamics
• Phase transitions
• Phonons