EN
The structural and magnetic properties of Dy_{1_{x}}Er_{x}Fe_{10}Si_{2} are investigated. X-ray analysis reveals that these compounds are of the tetragonal ThMn_{12} structure. In this structure the rare earth atoms occupy one crystallographic position 2(a). The unit cell contains 26 atoms. The spin reorientation temperature, T_{SR}, was measured from the temperature dependence of the initial susceptibility using an ac bridge of mutual inductance of the Harsthorn type. Dy^{+3} and Er^{+3} have opposite contributions to the entire magnetic anisotropy. The spin reorientation temperature is found to be about 271 K in DyFe_{10}Si_{2} and 48 K in ErFe_{10}Si_{2}. The values are discussed applying the crystal field model. The value of the rare earth-transition metal exchange coupling constant J_{RFe}/k_{B} derived from the mean-field model analysis of the Curie temperature is about -13 K. The Fe-Fe exchange integral is much higher and is equal to about 75 K.