Wavevector-dependent optical properties from wavevector-independent proper conductivity tensor Ronald Starke, René Wirnata, Giulio A.H. Schober, Nebahat Bulut and Jens Kortus Eur. Phys. J. B, 93 3 (2020) 54 Published online: 23 March 2020 DOI: 10.1140/epjb/e2019-90569-0