I need to find and invertable matrix P

Then a matrix C with the form:

|a -b|

|b a |

this comes from complex eigenvalues, and the formula

A= PC(P^-1)

my problem is

|5 -2|

|1 3 |

is the matrix

for the eigenvalues i got 4 +- 2i.

now i have to find eigenvectors and the C matrix

Can you help?