Structural and magnetic properties of Sc1.1Fe3.9Al8 alloy

► The magnetic structure of the Sc1.1Fe3.9Al8 alloy forms a double cycloid. ► The magnetic moments rotating according to the incommensurate in-plane wave vector. ► The propagation wave vector q→=(q⊥,q⊥,0) with q⊥ equal to 0.131(2) is temperature independent up to 160 K. ► The dominant antiferromagnetic Fe-Fe coupling in the basal plane exists up to about 230 K. ► The magnetic moment of iron is of the order of 0.9 μB at 4 K.