The new compounds MgMnGe, MgMnSn, CaMnSi, CaMnSn, and SrMnSn were prepared by reaction of the elements. They crystallize tetragonally with the anti-PbFCl type structure (space group P4/nmm). The lattice constants see "Inhaltsubersicht". Using a Faraday balance, magnetic measurements in the range 4.2 to 800 K were performed with the new substances and with the already known compounds CaMnGe, SrMnGe, and BaMnGe. They indicate metamagnetic behaviour at low temperatures. At high temperatures twodimensional magnetic interactions between the manganese atoms seem to persist. The construction of an unexpensive heating device for the Faraday balance is described.