  We present a systematic angle-resolved photoemission spectroscopy study of
the superconducting gap in FeSe. The gap function is determined in a full
Brillouin zone including all Fermi surfaces and kz-dependence. We find
significant anisotropy of the superconducting gap in all momentum directions.
While the in-plane anisotropy can be explained by both, nematicity-induced
pairing anisotropy and orbital-selective pairing, the kz-anisotropy requires
additional refinement of theoretical approaches.
