The quaternary compounds RE4Ni2InGe4 ( RE) Dy, Ho, Er, and Tm) were obtained as large single crystals in high yields from reactions run in liquid In. The title compounds crystallize in the monoclinic C2/m space group with the Mg5Si6 structure type with lattice parameters a = 15.420(2) angstrom, b = 4.2224(7) angstrom, c = 7.0191(11) angstrom, and beta = 108.589(2)degrees for Dy4Ni2InGe4, a = 15.373(4) angstrom, b = 4.2101(9) angstrom, c = 6.9935(15) angstrom, and beta = 108.600(3) for Ho4Ni2InGe4, a = 15.334(7) angstrom, b = 4.1937(19) angstrom, c = 6.975(3) angstrom, and beta = 108.472(7) for Er4Ni2InGe4, and a = 15.253(2) angstrom, b = 4.1747(6) angstrom, c = 6.9460(9) angstrom, and beta = 108.535(2) for Tm4Ni2InGe4. RE4Ni2InGe4 formed in liquid In from a melt that was rich in the rare-earth component. These compounds are polar intermetallic phases with a cationic rare-earth substructure embedded in a transition metal and main group matrix. The rare-earth atoms form a highly condensed network, leading to interatomic distances that are similar to those found in the elemental lanthanides themselves. The Dy and Ho analogues display two maxima in the susceptibility, suggesting antiferromagnetic ordering behavior and an accompanying spin reorientation. The Er analogue shows only one maximum in the susceptibility, and no magnetic ordering was observed for the Tm compound down to 2 K.