Two new compounds were synthesized by heating mixtures of the elements at 975-1025 K and characterized by single-crystal X-ray methods. CaZn 2 Si 2 (a=4.173(2) ( A, c=10.576(5) ( A) and EuZn 2 Ge 2 (a=4.348(2) ( A, c=10.589(9) ( A) crystallize in the ThCr 2 Si 2 -type structure (space group I4/mmm; Z=2). Magnetic susceptibility measurements of EuZn 2 Ge 2 show Curie-Weiss behavior with a magnetic moment of 7.85(5) l B /Eu and a paramagnetic Curie temperature of 10(1) K. EuZn 2 Ge 2 orders antiferromagnetically at T N =10.0(5) K and undergoes a metamagnetic transition at a low critical field of about 0.3(2) T. The saturation magnetization at 2 K and 5.5 T is 6.60(5) l B /Eu. 151 Eu M. ossbauer spectroscopic experiments show one signal at 78 K at an isomer shift of À11.4(1) mm/s and a line width of 2.7(1) mm/s compatible with divalent europium. At 4.2 K full magnetic hyperfine field splitting with a field of 26.4(4) T is detected. The already known compounds CaM 2 Ge 2 (M: Mn-Zn) also crystallize in the ThCr 2 Si 2 -type structure. Their MGe 4 tetrahedra are strongly distorted with M=Ni and nearly undistorted with M=Mn or Zn. According to LMTO electronic band structure calculations, the distortion is driven by a charge transfer from M-Ge antibonding to bonding levels. # 2002 Elsevier Science (USA)