Orbital Ordering in the Charge Density Wave Phases of BaNi2(As1-xPx)2

We use resonant x-ray scattering at the nickel L2,3 edges to investigate the interplay between orbital degrees of freedom and charge density waves (CDWs) in the superconductor BaNi2(As1-xPx)2. Both the incommensurate and commensurate CDWs in this system exhibit strong resonant enhancement with distinct energy and polarization dependencies, indicative of orbital ordering. Azimuthal-angle-dependent measurements reveal a lowering of the local Ni site symmetry, consistent with monoclinic or lower point group symmetry. The scattering signatures of both CDWs are dominated by contributions from Ni dxz,yz orbitals, with similar orbital character despite their distinct wave vectors. These findings point to a shared orbital-driven formation mechanism and provide new insight into the symmetry breaking and orbital and nematic fluctuations in the high-temperature regime of the superconductor BaNi2(As1-xPx)2.