  Quantum oscillation measurements in the new unconventional superconductor
YFe$_2$Ge$_2$ resolve all four Fermi surface pockets expected from band
structure calculations, which predict an electron pocket in the Brillouin zone
corner and three hole pockets enveloping the centers of the top and bottom of
the Brillouin zone. The carrier masses are uniformly renormalized by about a
factor of five and broadly account for the enhanced heat capacity Sommerfeld
coefficient $\simeq 100$ mJ/molK$^2$. Our data highlight the key role of the
electron pocket, which despite its small volume accounts for about half the
total density of states, and point towards a predominantly local mechanism
underlying the mass renormalization in YFe$_2$Ge$_2$.
