RECENTLY, superconductivity at >130 K was reported1,2 in multiphase samples of the compound system HgBa2Ca n-1CunO2n+2+δ (Hg-12(n-l)n) with n Combining double low line 1, 2, 3,.... Single-phase Hg-1223 was subsequently synthesized and found to be superconducting at a record temperature of 135 K (ref. 3). It remains to be seen if a much higher transition temperature (T c) than 135K can be achieved in this compound system. The application of pressure generally increases the Tc of underdoped layered cuprates, with a pressure derivative of Tc that decreases with increasing doping4,5. Preliminary studies on Hg-12236 showed a pressure-induced increase in Tc without any sign of saturation up to 17 kbar. Here we report the observation of superconductivity at up to 153 K in Hg-1223 at 150 kbar, with a main transition at 147 K. This observation provides an indication that superconductivity at >150 K may be possible in this system at ambient pressure, if suitable forms of chemical substitution can be found.
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