Tetragonal R(Fe,M)12 compounds (R=rare earth, M transition metal or Si), with the ThMn12 structure, are good candidates as permanent magnet materials with reduced R content. However, some stability issues have to be overcome. Typical stabilizing elements (M=Ti, V, Mo…) have a preference for the occupation of the 8i site in the structure, while Si has a preference for the 8j and 8f sites, leaving the 8i site (which corresponds to the largest Fe moment for the ThMn12 structure) fully occupied by Fe, so the RFe10Si2 shows higher saturation magnetization (~130 Am2/kg) than other compounds with a different stabilizing element. However, Si reduces the value of the Curie temperature and magnetic anisotropy, and then has a limited applicability. This drawback can be overcome by nitrogenation, which is known to enhance the Curie temperature and the anisotropy field of ThMn12 type of alloys.