It is well known that the breakthrough of Bednorz and Müller 1 in discovering superconductivity in (La, Ba)2CuO 4 was inspired in part by their knowledge of the superconducting properties of Ba(Pb, Bi)O3 (ref. 2). With a transition temperature, Tc, of ∼12 K, that compound was not generally considered anomalous despite the fact that its Tcis 3-5 times higher than that of traditional superconductors with comparable density of states3-5. The increases in Tc for copper-oxide-based materials continue to generate worldwide excitement, but from both a chemical and theoretical point of view it would also be exciting if high-Tcsuperconductivity were observed in another class of materials. Here we report the results of experiments leading us to the single-phase perovskite Ba0.6K 0.4BiO3, which has a magnetically determined onset temperature of 29.8 K-a Tc considerably higher than that of conventional superconductors and surpassed only by copper-containing compounds. Superconductivity in this compound occurs within the framework of a three dimensionally connected bismuth-oxygen array. These results suggest that further research toward exploring the limiting Tcs for bismuth-oxide-based, high-temperature superconductors might be fruitful.
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