Synthesis and Properties of YbB2
  We report temperature and field dependent measurements of the magnetic susceptibility, specific heat and resistivity of sintered YbB2 pellets, prepared via two distinct reaction routes, utilizing different temperatures, pressures and sintering times. Sample behavior is affected by the preparation procedure, as a consequence of different secondary phases, most of which were identified via x-ray diffraction. These experiments show that YbB2 is a metal with the Yb atoms in or very close to their 3+ state. YbB2 appears to order anti-ferromagnetically at TN ~ 5.6 K, which can be considered a relatively high ordering temperature for an ytterbium-based intermetallic compound. 
M.A. Avila, S.L. Bud'ko, C. Petrovic, R.A. Ribeiro, P.C. Canfield,   A.V. Tsvyashchenko, L.N. Fomicheva