[en] The effects of the substitution of Cr with Co on microstructure, phase composition, structure, magnetic, and electrical properties in $\text{F}{\text{e}}_2\text{C}{\text{r}}_{1-<!--\; ???\; -->x}\text{C}{\text{o}}_x\text{Si}$ (0  ⩽  x  ⩽  1) alloys was investigated to identify the compositions with the potential to exhibit half-metallicity. The microstructural and structural studies revealed that only $\text{F}{\text{e}}_2\text{C}{\text{r}}_{1-<!--\; ???\; -->x}\text{C}{\text{o}}_x\text{Si}$ alloys with x  ⩾  0.5 exhibited the desired single phase L2₁ full Heusler alloy structure. Both the saturation magnetization (M _s) and Curie temperature (T _C) were found to increase with the increase in Co concentration. The experimentally measured M _s values are in good agreement with the Slater–Pauling rule. The electrical resistivity measurements in the temperature range 10–300 K gives indirect evidence of half-metallic behaviour in these alloys at low temperatures. The temperature range in which the half-metallic behaviour was observed also increased with an increase in Co concentration. (paper)