Akm[k_,m_]:=Piecewise[{{(Eag + 2*(Eeu1 + Eeu2))/5, k == 0 && m == 0}, {Eag + Eeu1 - 2*Eeu2, k == 2 && m == 0}, {-3*Sqrt[7/5]*(Meu1 - I*Meu2), k == 4 && m == -3}, {(3*(3*Eag - 4*Eeu1 + Eeu2))/5, k == 4 && m == 0}, {3*Sqrt[7/5]*(Meu1 + I*Meu2), k == 4 && m == 3}}, 0]