Akm[k_,m_]:=Piecewise[{{0, (k != 4 && (k != 2 || m != 0)) || (m != -3 && m != 0 && m != 3)}, {(5*(Sqrt[5]*Ma2u1 + 4*Ma2u2 - 4*Meu1))/Sqrt[21], k == 2 && m == 0}, {(1/2 - I/2)*Sqrt[3]*(2*Ma2u1 + Sqrt[5]*Ma2u2), k == 4 && m == -3}, {-(Sqrt[3/7]*(8*Sqrt[5]*Ma2u1 + 11*Ma2u2 - 18*Meu1))/2, k == 4 && m == 0}}, (-1/2 - I/2)*Sqrt[3]*(2*Ma2u1 + Sqrt[5]*Ma2u2)]