Scaling of an anomalous metal-insulator transition in a two-dimensional system in silicon atB=0

We have studied the temperature dependence of resistivity, , for a two-dimensional electron system in silicon at low electron densities nₒ10^11 cm^-2, near the metal-insulator transition. The resistivity was empirically found to scale with a single parameter T₀, which approaches zero at some critical electron density n₂ and increases as a power T₀nₒ-n₂^ with =1. 60. 1 both in metallic (nₒ>n₂) and insulating (nₒn₂) regions. This dependence was found to be sample independent. We have also studied the diagonal resistivity at Landau-level filling factor =3/2, where the system is known to be in a true metallic state at high magnetic field and in an insulating state at low magnetic field. The temperature dependencies of resistivity at B=0 and =3/2 were found to be identical. These behaviors suggest a true metal-insulator transition in the two-dimensional electron system in silicon at B=0, in contrast with the well-known scaling theory.