AbstractThe novel nitrides (R1–xCa3+xN1–x/3)Bi2 (with R = La, Ce, Pr) crystallize in the K2[NiF4] structure type (I4/mmm, No. 139, Z = 2). Samples (La1–xCa3+xN1–x/3)Bi2 with x = 0.10, 0.05, 0.00, (Ce1–xCa3+xN1–x/3)Bi2 with x = 0.30, and (PrCa3N)Bi2 were obtained as single phase microcrystalline powders according to X‐ray diffraction and the crystal structure details were derived from Rietveld refinements based on X‐ray and neutron diffraction powder patterns. A partial order of R3+/Ca2+ on two crystallographic sites is governed by different ionic radii and charges. (La1–xCa3+xN1–x/3)Bi2 and (Ce1–xCa3+xN1–x/3)Bi2 exhibit small homogeneity ranges and typically a nitrogen deficiency. In contrast, for (PrCa3N)Bi2 no indications for a significant homogeneity range or deficiency of nitrogen was observed. (La1–xCa3+xN1–x/3)Bi2 with x = 0.05 is a diamagnet. X‐ray absorption spectroscopy at the CeL3‐edge as well as magnetic susceptibility measurements evidence that (Ce1–xCa3+xN1–x/3)Bi2 with x = 0.30 contains Ce3+ in the 4f1 configuration. According to electrical resistivity data, samples from all three systems are heavily doped semiconductors.