YbCo4Ge2 and YbNi5Ge3: two compounds with a stable trivalent, antiferromagnetically ordered Yb state

We investigated the magnetic properties of the two compounds YbCo4Ge2 and YbNi5Ge3 by means of magnetic susceptibility χ, specific heat Cp and electrical resistivity ρ measurements down to 0.5 K. Our results show that both compounds present a rather well localized, trivalent Yb state which undergoes a transition into an antiferromagnetic state at TN=2.7K (YbNi5Ge3) and TN=2.5K (YbCo4Ge2), respectively.