Transport properties of infinite-layerp-type cuprates

Previously we synthesized infinite-layer cuprates, ${\mathrm{Ca}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Li}}_{\mathit{x}}$ ${\mathrm{CuO}}_2$ with 0.2≤x≤0.45 and showed that Li ions entered the Ca site. These were the first hole-doped (or p-type) cuprates, to our knowledge, that contained square-coplanar fourfold-coordinated Cu ions (without Cu ions having apex oxygen ions). Here, we studied the transport properties of these cuprates and found that it was difficult to metallize them by means of conventional hole-doping techniques. In conjunction with the present experimental results, we discussed the electronic structure of high-${\mathit{T}}_{\mathit{c}}$ superconducting cuprates.