Akm[k_,m_]:=Piecewise[{{(Ea2u + Eb1u + Eb2u + 2*Eeu1 + 2*Eeu2)/7, k == 0 && m == 0}, {(5*(Ea2u - Eeu1 + Sqrt[15]*Meu))/7, k == 2 && m == 0}, {(-3*(2*Sqrt[70]*Eb1u - 2*Sqrt[70]*Eb2u - 3*Sqrt[70]*Eeu1 + 3*Sqrt[70]*Eeu2 - 2*Sqrt[42]*Meu))/56, k == 4 && (m == -4 || m == 4)}, {(3*(12*Ea2u - 14*Eb1u - 14*Eb2u + 9*Eeu1 + 7*Eeu2 - 2*Sqrt[15]*Meu))/28, k == 4 && m == 0}, {(-13*Sqrt[3]*(4*Sqrt[42]*Eb1u - 4*Sqrt[42]*Eb2u + 5*Sqrt[42]*Eeu1 - 5*Sqrt[42]*Eeu2 + 2*Sqrt[70]*Meu))/560, k == 6 && (m == -4 || m == 4)}, {(13*(40*Ea2u + 12*Eb1u + 12*Eb2u - 25*Eeu1 - 39*Eeu2 - 14*Sqrt[15]*Meu))/280, k == 6 && m == 0}}, 0]