Akm[k_,m_]:=Piecewise[{{(Ea1u + Ea2uA + Ea2uB + 2*Eeu1 + 2*Eeu2)/7, k == 0 && m == 0}, {(-5*(5*Ea1u + 5*Ea2uA - 4*Ea2uB - 6*Eeu1))/28, k == 2 && m == 0}, {((-3*I)*(3*Ma2u - 2*Meu))/Sqrt[14], k == 4 && (m == -3 || m == 3)}, {(3*(3*Ea1u + 3*Ea2uA + 2*(3*Ea2uB + Eeu1 - 7*Eeu2)))/14, k == 4 && m == 0}, {(13*Sqrt[33/7]*(Ea1u - Ea2uA))/20, k == 6 && (m == -6 || m == 6)}, {((13*I)/5)*Sqrt[3/14]*(Ma2u + 3*Meu), k == 6 && (m == -3 || m == 3)}, {(-13*(Ea1u + Ea2uA - 20*Ea2uB + 30*Eeu1 - 12*Eeu2))/140, k == 6 && m == 0}}, 0]