Isostructural ordering in a decahydrate of aluminomethylammonium alums

Measurements are performed of the temperature relations of the dielectric and pyroelectric properties of crystals of decahydrates of aluminomethylammonium alums near a temperature of 145 K. Based on the acquired results a conclusion is drawn about the existence at 145.3 K of an isostructural dipole ordering which may be associated with ordering of the $H_2O$ molecules or of the $CH_3NH_3$ groups.