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HoNiSi₃ is an intermetallic compound which crystallizes in an orthorhombic structure (Cmmm space group). Specific heat measurements show two clearly distinct phase transitions, T_N1 = 6.3 K and T_N2 = 10.4 K, marked by well-defined λ-shape anomalies. In addition, magnetic susceptibility measurements revealed that the magnetic response at T_N1 happens when the field is applied along the c axis, while at T_N2 happens with the field applied along with a.¹ In order to shed light onto the intriguing magnetic behavior of HoNiSi₃, we have performed polarized resonant X-ray magnetic diffraction experiments. Our results show magnetic intensities at the same position of nuclear Bragg peaks below T_N1 and T_N2. This indicates a magnetic structure having a + - + - stacking pattern of ac ferromagnetic planes along b with propagation vector k = [0,0,0]. Also, we discriminate the signal from different projections of the total magnetic moment and infer that at temperatures between T_N1 and T_N2 the ordered magnetic moment points along the a-axis, while below T_N1 an additional component along c arises, in agreement with magnetic susceptibility measurements.

[1] F. R. Arantes et al., Phys. Rev. Mater. 2 044402 (2018).