First measurement of ψ(3686)̄ K⁺ Σ*(1385)⁰ + c.c. and ψ(3686)̄ K*(892)⁰ Σ⁺ + c.c.

Based on a sample of (2712.4 ± 14.3) × 10⁶ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider, we report the first observation of the decays ψ(3686)̄ K⁺ Σ*(1385)⁰+c.c. and ψ(3686)̄ K*(892)⁰ Σ⁺ + c.c.. The corresponding branching fractions are determined to be B(ψ(3686)̄K⁺Σ*(1385)⁰+c.c.)=(3.94±0.15stat.±0.24syst.)×10⁻⁵ and B(ψ(3686)̄K*(892)⁰Σ⁺+c.c.)=(4.93±0.14stat.±0.30syst.)×10⁻⁵. Furthermore, we search for the hidden-strange pentaquark candidates Nₓ(1875) and Nₓ(2100) in the invariant mass spectra of K⁺ Σ*(1385)⁰ and K*(892)⁰ Σ⁺, respectively. No significant signals are observed and the upper limits on the branching fractions at the 90% confidence level are B(ψ(3686)̄Nₓ(1875)̄K⁺Σ*(1385)⁰)<1.58×10⁻⁶ and B(ψ(3686)̄Nₓ(2100)̄K*(892)⁰Σ⁺)<3.09×10⁻⁷.