  We report inelastic neutron scattering measurements from our newly
synthesized single crystals of the structurally metastable antiferromagnetic
pyrochlore Yb$_{2}$Ge$_{2}$O$_{7}$. We determine the four symmetry-allowed
nearest-neighbor anisotropic exchange parameters via fits to linear spin wave
theory supplemented by fits of the high-temperature specific heat. The exchange
parameters so-determined are strongly correlated to the values determined for
the $g$-tensor components, as previously observed for the related Yb pyrochlore
Yb$_{2}$Ti$_{2}$O$_{7}$. To address this issue, we directly determined the
$g$-tensor from electron paramagnetic resonance of 1% Yb-doped
Lu$_{2}$Ge$_{2}$O$_{7}$, thus enabling an unambiguous determination of the
exchange parameters. Our results show that Yb$_{2}$Ge$_{2}$O$_{7}$ resides
extremely close to the classical phase boundary between an antiferromagnetic
$\Gamma_5$ phase and a splayed ferromagnet phase. By juxtaposing our results
with recent ones on Yb$_{2}$Ti$_{2}$O$_{7}$, our work illustrates that the Yb
pyrochlore oxides represent ideal systems for studying quantum magnets in close
proximity to classical phase boundaries.
