Low-temperature resistivity of Yb in Au, Ag, and Au-Ag alloys

We present resistivity measurements on ${\left({\mathrm{Au}}_x{\mathrm{Ag}}_{100-x}\right)}_{100-y}{\mathrm{Yb}}_y$ which cover the concentration range between $x=0\mathrm{} \mathrm{and} 100$ at.%, and $y=0\mathrm{} \mathrm{and} 2$ at.%. The resistivity minima observed are found to be a combination of two mechanisms, which can be separated only by a suitable heat treatment. The first effect is due to the Yb behaving as a solid solution and is explained in terms of the shift of the Fermi level as the host's composition is varied. The second effect results form the presence of intermetallic phases inside the matrix, essentially Yb${\mathrm{Au}}_3$. Of these two mechanismes, that due to the intermetallic phase dominates. The resistivity of some intermetallic compounds $\mathrm{Yb}{\mathrm{Au}}_x$ has also been measured and found to show resistivity minima, larger than any of those observed in the (AuAg)Yb system.