Observation of ψ3686→K−Λ1520Ξ¯+ + c.c.

Based on (2712.4 ± 14.3) × 10⁶ψ(3686) events collected at the BESIII detector operating at the BEPCII collider, we present the first observation of the decay ψ3686→K−Λ1520Ξ¯+ + c.c. The product branching fraction Bψ3686→K−Λ1520Ξ¯++c.c.×BΛ1520→pK− is measured to be (9.47 ± 0.75 ± 0.97) × 10⁻⁷, where the first uncertainty is statistical and the second systematic.