  Here we report on a new kind of compound, X{\delta}Ir4X12-{\delta} (X = P,
As), the first hole-doped skutterudites superconductor. We provide atomic
resolution images of the caging As atoms using scanning transmission electron
microscopy (STEM). By inserting As atoms into the caged structure under a high
pressure, superconductivity emerges with a maximum transition temperature (Tc)
of 4.4 K (4.8 K) in IrAs3 (IrP3). In contrast to all of the electron-doped
skutterudites, the electronic states around the Fermi level in
X{\delta}Ir4X12-{\delta} are dominated by the caged X atom, which can be
described by a simple body-centered tight-binding model, implying a distinct
paring mechanism. Our density functional theory (DFT) calculations reveal an
intimate relationship between the pressure-dependent local-phonon mode and the
enhancement of Tc. The discovery of X{\delta}Ir4X12-{\delta} provides an arena
to investigate the uncharted territory of hole-doped skutterudites, and the
method proposed here represents a new strategy of carrier doping in caged
structures, without introducing extra elements.
