The invention relates to novel materials of the formula: AuM1vM2wM3XM4yM5ZO2 wherein A comprises one or more alkali metals selected from lithium, sodium and potassium; M1 is nickel in oxidation state +2 M2 comprises a metal in oxidation state +4 selected from one or more of manganese, titanium and zirconium; M3 comprises a metal in oxidation state +2, selected from one or more of magnesium, calcium, copper, zinc and cobalt; M4 comprises a metal in oxidation state +4, selected from one or more of titanium, manganese and zirconium; M5 comprises a metal in oxidation state +3, selected from one or more of aluminum, iron, cobalt, molybdenum, chromium, vanadium, scandium and yttrium; further wherein U is in the range 1