Compound  is a zonal metamagnet. It was found that partial substitution of cobalt for aluminum in  leads to a decrease in the matamagnetic transition field and the emergence of weak zonal ferromagnetism in the system at . This can significantly modify the character of the effect of rare-earth impurities on the –subsystem. To exclude the effect of the crystal­li­ne field, gadolinium was used as a magnetizing element. Hence the magne­tic properties of the system  were studied in this work. We confined ourselves to the aluminum concentration range () in the limits of which initial compounds  are paramagnets and undergo a metamagnetic transition in the field. It is shown that, with an increase in the concentration of  (with constant concentration of ), the transition from paramagnetism to ferromagne­tism takes place. When the content of  increases, the area of ferro­magnetism expands, and the paramagnetic state area shrinks. The behavior of the compounds under study in the field depends on the ratio between the degrees of magnetization of cobalt  and gadolinium  subsystems. If in a weak field is greater than , gadolinium impurities shift the metamagnetic transition field towards weak fields, as the molecular field acting on cobalt from the gadolinium subsystem is summed with the external magnetic field . In case  in a weak field is smaller than ,  and  are directed anti­para­llel to each other.