  We carried out electrical resistivity experiments on (Yb,La)Rh2Si2 and on
Yb(Rh,Ir)2Si2 under pressure and in magnetic fields. YbRh2Si2 exhibits a weak
antiferromagnetic transition at atmospheric pressure with a N\'eel temperature
of only T_N = 70 mK. By applying a small magnetic field T_N can be continuously
suppressed to T=0 at B_c = 60 mT (B_|_c) driving the system to a quantum
critical point (QCP). On applying external pressure the magnetic phase is
stabilized and T_N(p) is increasing as usually observed in Yb-based
heavy-fermion metals. Substituting Yb by La or Rh by Ir allows to create a
negative chemical pressure, La (Ir) being smaller than Yb (Rh), and eventually
to drive YbRh2Si2 to a pressure controlled QCP. In this paper we compare the
effect of external hydrostatic pressure and chemical substitution on the
ground-state properties of YbRh2Si2.
