  We investigated the occurrence and nature of superconductivity in single
crystals of YFe$_2$Ge$_2$ grown out of Sn flux by employing x-ray diffraction,
electrical resistivity, and specific heat measurements. We found that the
residual resistivity ratio (RRR) of single crystals can be greatly improved,
reaching as high as $\sim$60, by decanting the crystals from the molten Sn at
$\sim$350$^\circ$C and/or by annealing at temperatures between 550$^\circ$C and
600$^\circ$C. We found that samples with RRR $\gtrsim$ 34 showed resistive
signatures of superconductivity with the onset of the superconducting
transition $T_c\approx1.4$ K. RRR values vary between 35 and 65 with, on
average, no systematic change in $T_c$ value, indicating that systematic
changes in RRR do not lead to comparable changes in $T_c$. Specific heat
measurements on samples that showed clear resistive signatures of a
superconducting transition did not show any signature of a superconducting
phase transition, which suggests that the superconductivity observed in this
compound is either some sort of filamentary, strain stabilized
superconductivity associated with small amounts of stressed YFe$_2$Ge$_2$
(perhaps at twin boundaries or dislocations) or is a second crystallographic
phase present at levels below detection capability of conventional powder x-ray
techniques.
