Element-specific x-ray resonant magnetic scattering investigations were performed to determine the magnetic structure of Eu in EuRh 2 As 2 . In the temperature range from 46 K down to the lowest achievable temperature of 6 K, an incommensurate antiferromagnetic ͑ICM͒ structure with a temperature-dependent propagation vector Ϸ͑0 0 0.9͒ coexists with a commensurate antiferromagnetic ͑CM͒ structure. Angulardependent measurements of the magnetic intensity indicate that the magnetic moments lie in the tetragonal basal plane and are ferromagnetically aligned within the a-b plane for both magnetic structures. The ICM structure is most likely a spiral-like magnetic structure with a turn angle of ϳ162°͑0.9͒ between adjacent Eu planes in the c direction. In the CM structure, this angle is 180°. These results are consistent with bandstructure calculations which indicate a strong sensitivity of the magnetic configuration on the Eu valence.The complex interplay among superconductivity, magnetism, and structural instabilities in AFe 2 As 2 ͑A = Ba, Sr, Ca, and Eu͒ pnictides upon chemical substitution or under applied pressure has generated a great deal of recent attention and research activity. 1-7 Related isostructural compounds such as BaRh 2 As 2 , BaMn 2 As 2 , and EuRh 2 As 2 ͑Refs. 8-10͒ have also been synthesized and studied in an attempt to increase significantly superconducting transition temperatures and to understand the role of Fe in the Fe-As layers as well as the A site in promoting superconductivity. The metallic compound EuRh 2 As 2 shows a plethora of interesting physical properties such as giant magnetoresistance and a strong reduction in the electronic specific-heat coefficient with applied field in the antiferromagnetic state. 10 The reported intermediate valence of 2.13͑2͒ for Eu ͑Ref. 10͒ adds further interest as it may be tuned by applied pressure or temperature. 11,12 Since Eu 2+ ions carry a magnetic moment with spin S =7/ 2 while Eu 3+ does not have a permanent magnetic moment, EuRh 2 As 2 may be an excellent model system to study the complex interplay between valence and magnetism in the "122" pnictides.EuRh 2 As 2 crystallizes in the ThCr 2 Si 2 -type tetragonal structure with space group I4 / mmm ͑Ref. 13͒ and lattice parameters a = 4.075 Å and c = 11.295 Å at T = 298 K. 10 Specific-heat and magnetization data indicate that the Eu moments order antiferromagnetically below T N =46 K. 10 The magnetic susceptibility parallel to the c axis increases below T N and decreases when measured perpendicular to the c axis. 10 This indicates that the moments are primarily aligned in the basal a-b plane. Nevertheless, the microscopic details of the magnetic structure are, as yet, unknown. Here, we report on the magnetic ordering of Eu moments in EuRh 2 As 2 studied by x-ray resonant magnetic scattering ͑XRMS͒. 14 For the present measurements, this technique offers several advantages over neutron scattering due to the large neutron absorption cross section of the natural isotope 152 Eu. Moreover, the elemental...