2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/213432We consider the superspace of D=3, N=5 supersymmetry using SO(5)/U(2) harmonic coordinates. Three analytic N=5 gauge superfields depend on three vector and six harmonic bosonic coordinates and also on six Grassmann coordinates. Decomposition of these superfields in Grassmann and harmonic coordinates yields infinite-dimensional supermultiplets including a three-dimensional gauge Chern-Simons field and auxiliary bosonic and fermionic fields carrying SO(5) vector indices. The superfield action of this theory is invariant with respect to D=3, N=6 conformal supersymmetry realized on N=5 superfields.Latex file, 17 pages, v2 with minor changes, v3 journal versionHigh Energy Physics - Theorytext