Studies of dilute Fe-57 as a diamagnetic probe in RMn(2)Si(2-x)Ge(x) (
R = La, Sm, Gd) show that the ferromagnetic compounds, with R = La, Sm
and T-c similar to 320 K, are antiferromagnets above T-c, with T-N si
milar to 450 K, similar to T-N in the heavy rare earth compounds. At t
he phase transitions, changes in the easy magnetization axes are obser
ved.