  We present the first demonstration of vortices in an electron-type cuprate
superconductor, the highest $T_c$ (= 43 K) electron-type cuprate
$Sr_{0.9}La_{0.1}CuO_2$. Our spatially resolved quasiparticle tunneling spectra
reveal a hidden low-energy pseudogap inside the vortex core and unconventional
spectral evolution with temperature and magnetic field. These results cannot be
easily explained by the scenario of pure superconductivity in the ground state
of high-$T_c$ superconductivity.
