  Temperature and applied magnetic field dependent magnetization measurements
on 34 single crystalline samples of (R, R',R''...)Ni2Ge2 compounds (R, R', R'',
etc. being primarily Gd-Lu, Y), were made. These measurements reveal that,
despite extremes in local moment anisotropy, the average de Gennes parameter is
a remarkably good predictor of the paramagnetic to antiferromagnetic ordering
temperature. In addition, the pronounced metamagnetic phase transitions seen in
the low temperature phase of TbNi2Ge2 are found to be remarkably robust to high
substitution levels of Gd and 25% substitutions of other heavy rare earths.
