We have studied the effect of Ge substitution and pressure on the heavy-fermion superconductor ${\text{CePt}}_3\text{Si}$. Ge substitution on the Si site acts as negative chemical pressure leading to an increase in the unit-cell volume but also introduces chemical disorder. We carried out electrical resistivity and ac heat-capacity experiments under hydrostatic pressure on ${\text{CePt}}_3{\text{Si}}_{1-x}{\text{Ge}}_x$ $\left(x=0,0.06\right)$. Our experiments show that the suppression of superconductivity in ${\text{CePt}}_3{\text{Si}}_{1-x}{\text{Ge}}_x$ is mainly caused by the scattering potential, rather than volume expansion, introduced by the Ge dopants. The antiferromagnetic order is essentially not affected by the chemical disorder.

• Received 8 March 2010

DOI:https://doi.org/10.1103/PhysRevB.81.180511