Electrical-resistivity (\ensuremath{\rho}) behavior in the vicinity of the N\'eel temperature (${\mathit{T}}_{\mathit{N}}$) of the pseudoternary alloys R${\mathrm{Cu}}_{2\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ni}}_{\mathit{x}}$${\mathrm{Si}}_{2}$ (R=Pr, Gd, and Dy) and ${\mathit{R}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{La}}_{\mathit{x}}$${\mathrm{Cu}}_{2}$${\mathrm{Si}}_{2}$ (R=Pr and Gd) is reported. There is an increase in \ensuremath{\rho} just below ${\mathit{T}}_{\mathit{N}}$ in several alloys, followed by the usual decrease at lower temperatures due to the loss of spin-disorder contribution. We attribute this rise in \ensuremath{\rho} to the formation of an energy gap at the Fermi surface due to antiferromagnetic ordering.