BaNi$_2$As$_2$ can be seen as the non-magnetic analogue of the prototype material of the Fe-based superconductors BaFe$_2$As$_2$. At ambient conditions both materials share the same tetragonal I4/mmm structure. At lower temperatures (T≈150K) an incommensurate charge density wave (I-CDW) was found. The I-CDW survives a distortion towards an orthorhombic phase (T=142K) before it is replaced by a commensurate CDW below a triclinic transition (T=137K). Below T$_c$=0.7K the material gets superconducting. The different orders and structural phases can be tuned by substitution e.g. by Sr, Co or P. Recent investigations of the Sr-substituted system give evidence of electronic nematic fluctuations and propose the system as electronic tunable nematic system. The interplay of the different orders in BaNi$_2$As$_2$ and orbital structure of the charge density waves remain unclear. We propose to investigate the orbital structure of the CDWs by a detailed REXS experiment at the Ni-L3 edge.

The experimental data included here were measured at the XUV diffractometer of beamline UE46-PGM-1 at BESSY II.

All raw and alignment scans are included in a single file in the format created and used by SPEC. Additionally, pictures of the mounting and of the different rotations are included.

The raw data includes several test samples, as well as phosphor-substituted samples. The relevant sample is sample 3 in the naming of the experiment.

The experimental data included here were measured at the XUV diffractometer of beamline UE46-PGM-1 at BESSY II.