A comparison is made of some low-temperature properties of CePt2Si2, CePtAuSi2 and CeAu2Si2. New experimental data on the specific heat, electrical resistivity and magnetic susceptibility of CePtAuSi2, together with published results on the other compounds, reveal that the electronic ground state in these materials varies in a very significant way. In-between local-moment behaviour in CeAu2Si2 and a Kondo-type ground state in CePt2Si2, CePtAuSi2 forms a heavy-electron state at low temperatures. © 1991.