The results of magnetization, heat-capacity, and electrical resistivity (rho) studies of the compounds, RMAs2 (R= Pr and Sm; M= Ag, Au), crystallizing in HfCuSi2-derived structure are reported. PrAgAs2 orders antiferromagnetically at T_N= 5 K. The Au
analogue, however, does not exhibit long range magnetic order down to 1.8 K. We infer that this is due to subtle differences in their crystallographic features, particularly noting that both the Sm compounds with identical crystal structure as that of former order magnetically nearly at the same temperature (about 17 K). It appears that, in PrAgAs2, SmAgAs2, and SmAuAs2, there is an additional magnetic transition at a lower temperature, as though the similarity in the crystal structure results in similarities in magnetism as well. The rho for PrAgAs2 and PrAuAs2 exhibits negative temperature coefficient in some temperature range in the paramagnetic state. SmAuAs2 exhibits magnetic Brillouin-zone gap effect in rho at T_N, while SmAgAs2 shows a well-defined broad minimum well above T_N around 45 K. Thus, these compounds reveal interesting magnetic and transport properties.
