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)*(-2*Sqrt[3]*Ma2u1 + Sqrt[15]*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)*(-2*Sqrt[3]*Ma2u1 + Sqrt[15]*Ma2u2)]