"thanum, a lanthanide series element, boron, aluminum, gallium, indium, thallium, silicon, germanium, tin, lead, magnesium, calcium, strontium, and barium, and M2 is a metal selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, osmium, cobalt, nickel, zinc, cadmium, scandium, yttrium, lanthanu" . . . . . . . . . .