The syntheses and the characterization of two 17-atom endohedral Ge clusters, [Co₂@Ge₁₇]⁶⁻ (1a) and [Ni₂@Ge₁₇]⁴⁻ (2a), are reported. The anions 1a and 2a, which close the gap between the known 16- and 18-atom Ge clusters, are investigated by single crystal X-ray diffraction and by quantum chemical calculations. The structures mark a new example on the pathway for cluster growth towards larger clusters with icosahedral symmetry. Furthermore, the [Co@Ge₁₀]³⁻ anion (3a) is obtained from liquid ammonia.