First observation of J/\psi and \psi(2S) decaying to n K^0_S\bar\Lambda +c.c

The decays of $\text{jpsi}$ and $\text{psip}$ to $n{K}_S^0\bar{\mathrm{\Lambda }}+c\mathrm{.}c\mathrm{.}$ are observed and measured for the first time, and the perturbative QCD ``12%‘’ rule is tested, based on $5.8\times {10}^7$ $\text{jpsi}$ and $1.4\times {10}^7$ $\text{psip}$ events collected with BESII detector at the Beijing Electron-Positron Collider. No obvious enhancement near $n\bar{\mathrm{\Lambda }}$ threshold in $\jpsi \to {n}{K^0_S}\bar{\Lambda}+c.c.$ is observed, and the upper limit on the branching ratio of $\text{jpsi}\to K_S^{0}X,X\to n\bar{\mathrm{\Lambda }}$ is determined.