First observation of the decay ${\chi }_{cJ}\to {\mathrm{\Sigma }}^{+}\bar{p}{K}_S^0+c\mathrm{.}c\mathrm{.}(J=0,1,2)$

Using E1 radiative transitions $\psi (3686)\to \gamma {\chi }_{cJ}$ from a sample of $(448.1\pm 2.9)\times {10}^6$ $\psi (3686)$ events collected with the BESIII detector, the decays $\chi_{cJ}\to \Sigma^{+}\bar{p}K_{S}^{0}+c.c.~(J = 0, 1, 2)$arestudied\mathrm{.}Thedecaybranchingfractionsaremeasuredtobe$$\mathcal{B}$(\chi_{c0}\to \Sigma^{+}\bar{p}K_{S}^{0}+c.c.) = (3.52 \pm 0.19\pm 0.21)\times10^{-4}$,$$\mathcal{B}$(\chi_{c1}\to \Sigma^{+}\bar{p}K_{S}^{0}+c.c.) = (1.53 \pm 0.10\pm 0.08)\times10^{-4}$,and$$\mathcal{B}$(\chi_{c2}\to \Sigma^{+}\bar{p}K_{S}^{0}+c.c.) = (8.25 \pm 0.83 \pm 0.49)\times10^{-5}$, where the first and second uncertainties are the statistical and systematic ones, respectively. No evident intermediate resonances are observed in the studied processes.