Data for the manuscript “Spontaneous cycloidal order mediating a spin-reorientation transition in a polar metal" by C. D. Dashwood, L. S. I. Veiga, Q. Faure, J. G. Vale, D. G. Porter, S. P. Collins, P. Manuel, D. D. Khalyavin, F. Orlandi, R. S. Perry, R. D. Johnson, and D. F. McMorrow, Phys. Rev. B 102, 180410(R) (2020).All the data is provided in text files, each containing a single header line followed by the data. All temperatures are in Kelvin, magnetic field strengths in Tesla, angles in degrees, and resistances in Ohms.The parent folder contains the in-plane resistivity and powder XRD data.Neutron scattering data is contained in the "Neutron" folder, with each file labelled by the magnetic field strength and Bragg peak (commensurate peak "001" or incommensurate satellite peak "d01").Resonant x-ray scattering data is contained in the "X-ray" folder, under four subfolders for the azimuthal dependences ("Azi_deps"), energy dependences ("E_deps"), reciprocal space scans ("H_scans") and theta scans ("Th_scans"). Files in all the subfolders are labelled by the temperature and Bragg peak (commensurate peak "005" or incommensurate satellite peak "d05"), followed by further labels for the x-ray polarisation ("sig-sig" or "sig-pi"), azimuthal angle ("psi90" or "psi180") and absorption edge ("L2" or "L3"). The azimuthal dependences folder also contains a file "Parameters" with the fitted values of Ma and Mb (defined in the manuscript) and their errors.