Unconventional bulk superconductivity in YFe${}_2$Ge${}_2$ single crystals

Using a new horizontal flux growth technique to produce high quality crystals of the unconventional superconductor YFe${}_2$Ge${}_2$ has led to a seven-fold reduction in disorder scattering, resulting in mm-sized crystals with residual resistivities $\simeq \text{SI}0.45\text{micro}\text{ohm}\text{centi}\text{meter}$, resistivity ratios $\simeq 430$ and sharp superconducting heat capacity anomalies. This enables searching multi-probe experiments investigating the normal and superconducting states of YFe${}_2$Ge${}_2$. Low temperature heat capacity measurements suggest a significant residual Sommerfeld coefficient, consistent with in-gap states induced by residual disorder as predicted for a sign-changing order parameter.