Reproducible resistance drop around 250K in superconducting Hg-compounds

We report here a stable and reproducible resistivity drop at near 250K in high pressure synthesized Hg-Ba-Ca-Cu-O compounds at 5 GPa. Temperatures of partial resistivity drop at 230 ∼ 253K in H-1223 depend on oxygen situation during the high pressure synthesis. Resistivity anomalies did not disappear after thermal cycling or with a larger measuring current after up to two months period.