Unusual magnetic behaviour of binary YbNi3 alloy

•A first report on the physical properties of the YbNi3 binary alloy.•Orthorhombic crystal structure with inequivalent Yb and Ni crystallographic positions.•Unusual magnetic behaviour among Yb compounds.•Similar energy scales of the magnetic and Kondo interactions with a value of TK = 6 K. Measurements on the magnetic, electronic transport and thermal properties of the binary YbNi3 alloy are reported. The results are consistent with a magnetic transition at 3.9 K of Ferrimagnetic nature, as established from the AC magnetic susceptibility and the field dependence of DC magnetization and specific heat at low temperatures. Moreover, magnetic and electrical resistivity measurements reveal the presence of an additional magnetic transition around 50 K. The unusual magnetic ground state for Yb compounds is explained by the presence of different inequivalent Yb and Ni crystallographic sites, within an orthorhombic structure of the PuNi3-type (space group R3¯m), with similar temperature scales of the magnetic and Kondo interactions (TK=6K). The results are also compared to those reported for other binary Yb-Ni and RNi3 (R-Rare Earth) alloys.