  We have systemically studied the effects of annealing temperature and alloy
composition on the structural and magnetic properties of bulk Ni$_{2}$MnGe and
Ni$_{2.1}$Mn$_{0.9}$Ge Heusler alloys. We have observed that both annealing
temperature and the alloy composition drastically alter the phases found in the
samples due to the presence of competing ternary phases. Annealing at 900 and
950 $^{\circ}$C for both alloy compositions facilitate the formation of
L2$_{1}$ Heusler phase. Nevertheless, formation of Ni$_{5}$Mn$_{4}$Ge$_{3}$ and
Ni$_{16}$Mn$_{6}$Ge$_{7}$ phases cannot be prevented for Ni$_{2}$MnGe and
Ni$_{2.1}$Mn$_{0.9}$Ge alloys, respectively. In order to estimate the magnetic
contribution of the Ni$_{5}$Mn$_{4}$Ge$_{3}$ impurity phase to that of the
parent Ni$_{2}$MnGe, we have also synthesized pure Ni$_{5}$Mn$_{4}$Ge$_{3}$
alloy. Antiferromagnetic nature of Ni$_{5}$Mn$_{4}$Ge$_{3}$ with low
magnetization response allows us to reveal the magnetic response of the
stoichiometric bulk Ni$_{2}$MnGe. Bulk Ni$_{2}$MnGe shows simple ferromagnetic
behavior with a Curie temperature of 300 K, in agreement with the previous
results on thin films. Despite the divergence of magnetization curves between
field cooled (FC) and field heated (FH) modes, stoichiometric Ni$_{2}$MnGe
alloy does not undergo a martensitic phase transition based on our variable
temperature x-ray diffraction experiments.
