${\mathrm{MoBe}}_{22}$ and ${\mathrm{WBe}}_{22}$ compounds belong to the binary $X{\mathrm{Be}}_{22}$ $(X=4d$ or 5$d$ metal) family of superconductors, whose critical temperature depends strongly on $X$. Despite the multiphase nature of these samples, it is possible to investigate the superconducting properties of ${\mathrm{MoBe}}_{22}$ and ${\mathrm{WBe}}_{22}$ at the macro- and microscopic level. A concurrent analysis by means of magnetization and heat-capacity measurements, as well as muon-spin spectroscopy $\left(\mu \mathrm{SR}\right)$ was implemented. At ambient pressure, both compounds enter the superconducting state below $2.6\pm 0.1$ K $\left({\mathrm{MoBe}}_{22}\right)$ and $4.1\pm 0.10$ K $\left({\mathrm{WBe}}_{22}\right)$ and show modest upper critical fields [$({\mu }_0{H}_{\text{c2}}\left(0\right)=48\pm 1$ mT and ${\mu }_0{H}_{\text{c2}}\left(0\right)=58\pm 1$ mT, respectively]. In ${\mathrm{WBe}}_{22}$, the temperature-dependent superfluid density suggests a fully gapped superconducting state, well-described by an $s$-wave model with a single energy gap. Heat-capacity data confirm that such a model applies to both compounds. Finally, ac magnetic susceptibility measurements under applied pressures up to 2.1 GPa reveal a linear suppression of the superconducting temperature, typical of conventional superconducting compounds.

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• Crystal defects
• Crystal forms
• Crystal structure
• High-pressure studies
• Pressure effects
• Solid-state chemistry
• Superconducting gap
• Superconducting order parameter
• Superconducting phase transition
• Crystal structures
• Crystal growth
• Muon spin relaxation & rotation
• Muon spin resonance
• Pressure techniques