  Itinerant and local moment magnetism have substantively different origins,
and require distinct theoretical treatment. A unified theory of magnetism has
long been sought after, and remains elusive, mainly due to the limited number
of known itinerant magnetic systems. In the case of the two such examples
discovered several decades ago, the itinerant ferromagnets ZrZn_2 and Sc_3In,
the understanding of their magnetic ground states draws on the existence of 3d
electrons subject to strong spin fluctuations. Similarly, in Cr, an elemental
itinerant antiferromagnet (IAFM) with a spin density wave (SDW) ground state,
its 3d character has been deemed crucial to it being magnetic. Here we report
the discovery of the first IAFM compound with no magnetic constituents, TiAu.
Antiferromagnetic order occurs below a Neel temperature T_N ~ 36 K, about an
order of magnitude smaller than in Cr, rendering the spin fluctuations in TiAu
more important at low temperatures. This new IAFM challenges the currently
limited understanding of weak itinerant antiferromagnetism, while providing
long sought-after insights into the effects of spin fluctuations in itinerant
electron systems.
