Why are alloys used for making standard resistance coils?

(N/A) Alloys like Manganin or Constantan are used for making standard resistance coils because they possess a very low temperature coefficient of resistivity.
This means that the electrical resistivity of these alloys changes very little with variations in temperature.
Since the resistance $R$ of a conductor is given by $R = \rho \frac{l}{A}$,where $\rho$ is the resistivity,$l$ is the length,and $A$ is the cross-sectional area,a nearly constant $\rho$ ensures that the resistance $R$ remains stable even if the ambient temperature fluctuates.
Therefore,they are ideal for maintaining precise resistance values in standard resistors.