The resistivity of a material is dependent on the temperature. Different materials do not exhibit the same dependence on temperatures.
ρT = ρ0 [1 + α (T–T0)]
where ρT is the resistivity at a temperature T and ρ0 is the same at a reference temperature T0. α is called the temperature co-efficient of resistivity, and from the dimension of α is (Temperature)–1.