temperature coefficient of resistance

If temperature coefficient of resistance of two different materials connected in series. What will be over all temperature coefficient of resuatance. If they are connected in parallel, then what wlii the over all value?

See this page for answers
http://hyperphysics.phy-astr.gsu.edu/‌hbase/electric/restmp.html#c3

Then plug those answers into this
http://hyperphysics.phy-astr.gsu.edu/%E2%80%8Chbase/electric/resis.html#c3

R1 = r1(T) : R1 is equal to the function of resistance of material 1 (r1) over temperature (T)
R2 = r2(T) : R2 is equal to the function of resistance of material 2 (r2) over temperature (T)

Series:
RT = r1(T) + r2(T) or
RT = R1 + R2 at a particular temperature T

Parallel:
1/RT = 1/r1(T) + 1/r2(T)
1/RT = 1/R1 + 1/R2 at a particular temperature T

See Mark's post for insight into what those resistance due to temperature functions might be (not always linear).

if it is series mean to add two diffrent value,if it is parallel mean divide over all value by 1

That means , wlill it be same like normal addition of series and parallel resistances?

One metal have a temperature coefficient of resistance of 0.0005 other one have 0.0045.

Shall I add like r1+r2 for series and r1r2/(r1+r2) for parallel operations respectively???

Yes. At a particular temperature, a resister has a particular value -- in other words, it's just a resistor. So, the formulas for series and parallel resistance apply. If the temperature changes and the resistor has a temperature coefficient other than 0, then the resistance will be different. but again, it is just a resistor, but with a different value, because the temperature changed. At the new temperature, once again, the formulas for series and parallel resistors will apply, only the total resistance will be different, because of the temperature change.