Electronic properties of the actinide metals at low temperatures

Abstract
The electrical resistivity and thermoelectric power of thorium, uranium, neptunium and plutonium have been measured down to liquid-helium and liquid-hydrogen temperatures. The resistivities are relatively high, especially those of neptunium and plutonium, while all the thermoelectric powers show complicated temperature relations. The temperature dependence of the resistance of $\alpha$-plutonium is abnormal, being characterized by a small negative temperature coefficient above 105 $^\circ$K and a large positive coefficient below this temperature. Some plutonium rich $\delta$-Pu+Al alloys also show similar behaviour. An explanation in terms of spin-disorder effects seems most reasonable, and it is suggested that both $\alpha$- and $\delta$-plutonium may be antiferromagnetic. The resistance-temperature curves of uranium and neptunium also are unusual in that the positive temperature coefficients decrease monotonically with rising temperature. Possible reasons for this have been discussed.

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