EN
Magnetization measurements were performed for intermetallic compounds GdNi_{5-x}Sn_{1+x} and TbNi_{5-x}Sn_{1+x} in the temperature range from 4.5 K to 280 K and in magnetic field up to 50 kOe. Complex magnetic phase diagram was revealed for both compounds. The results are discussed assuming three-sublattice magnetic structure and partial disordering of the structure.