[en] The single-phase compounds of R₂Fe_17-xAl_xC (x=0-8; R≡Ho, Y or Sm) were fabricated by arc melting. Their structural and magnetic properties have been investigated by means of X-ray diffraction and magnetization measurements. X-ray diffraction patterns demonstrate that all compounds have a single phase with a hexagonal Th₂Ni₁₇-type or a rhombohedral Th₂Zn₁₇-type structure. The substitution of Al atoms leads to increase in the lattice constants and the unit-cell volume. The Curie temperature is found to change slightly when x≤3 and then to decrease rapidly with increasing Al concentration. An approximately linear decrease in the saturation magnetization with increasing x is observed by the substitution of non-magnetic Al atoms. The compensation points are observed for the Ho₂Fe_17-xAl_xC samples with x≥5. Samples of Sm₂Fe_17-xAl_xC with x≤6 exhibit an easy c-axis anisotropy at room temperature. The room-temperature anisotropy field increases to about 119 kOe when x=2 and then decreases with increasing Al concentration. The substitution of Al for Fe in a small concentration will increase the anisotropy field of Sm₂Fe₁₇ carbides. This behaviour is the same as that of Ga and Si. (author)