Uranium ruthenium silicide (URu₂Si₂) is a

heavy fermion In solid-state physics, heavy fermion materials are a specific type of intermetallic compound, containing elements with 4f or 5f electrons in unfilled electron bands. Electrons are one type of fermion, and when they are found in such materials, t ...

alloy composed of

uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...

ruthenium Ruthenium is a chemical element with the symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to most other chemical ...

, and

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ta ...

. URu₂Si₂ has the same '122' tetragonal crystal structure as many other compounds of present condensed matter research. URu₂Si₂ is a superconductor with a

hastatic order Hastatic order is a fundamental way of breaking double "time-reversal" symmetry. It is present in the heavy-fermion compound URu2Si2. This order was dubbed ''hastatic'' from ''hasta'', the Latin word for "spear". Its cycle is twice as complex a ...

(HO) phase below a temperature of 17.5 K. Below this temperature, it is magnetic, and below about 1.5 K it superconducts. However, the nature of the ordered phase below 17.5K is still under debate despite a wide variety of scenarios that have been proposed to explain this phase.

References

Correlated electrons Superconductivity Silicides Uranium compounds Ruthenium compounds {{Inorganic-compound-stub