A systematic investigation of structure and intrinsic magnetic properties of the novel compoundsR3(Fe, T)29(R=Y,Ce, Nd, Sm, Gd, Tb, and Dy;T=Vand Cr) has been performed. The lattice constants and unit cell volume decrease with increasing the rare-earth atomic number fromR=Ndto Dy, except for Ce, reflecting the lanthanide contraction. The Curie temperature increases fromR=Ceto Gd and decreases from Gd to Dy, respectively, with increasing atomic number andGd3Fe29−xTxhas the highest Curie temperature for each series ofR3Fe29−xTx(T=Vor Cr) compounds. The saturation magnetization ofR3Fe29−xTxat 4.2 K decreases gradually fromR=Ndto Dy with increasing atomic number, except for Ce, in each series ofR3Fe29−xTx.It is suggested that the Ce ion inCe3Fe29−xTxis valence fluctuated which leads to the unusual magnetic properties. The spin reorientations of the easy magnetization direction ofR3Fe29−xTxare observed at around 230, 230, and 160 K forR=Nd,Sm, and Tb whenT=V,and at around 230 and 180 K forR=Ndand Tb whenT=Cr,respectively. First order magnetization processes are observed around 5.7 T forSm3Fe26.7V2.3and 4 T forSm3Fe24.0Cr5.0at 4.2 K, 2.0 T forTb3Fe28.0V1.0,and 2.3 T forTb3Fe28.0Cr1.0at room temperature. A phenomenological analysis shows that the saturation magnetization ofR3Fe29−xTxcompounds with a low T concentration can be roughly calculated based on a combination of those of the2:17Rand 1:12 units in a ratio of 1:1. ©1997 American Institute of Physics.