Akm[k_,m_]:=Piecewise[{{(Eau1 + Eau2 + Eau3 + 2*Eeu1 + 2*Eeu2)/7, k == 0 && m == 0}, {(-5*(5*Eau1 - 4*Eau2 + 5*Eau3 - 6*Eeu1))/28, k == 2 && m == 0}, {((-9*I)*Mau12 - 9*Mau23 - 6*Meu1 + (6*I)*Meu2)/Sqrt[14], k == 4 && m == -3}, {(3*(3*Eau1 + 6*Eau2 + 3*Eau3 + 2*Eeu1 - 14*Eeu2))/14, k == 4 && m == 0}, {((-9*I)*Mau12 + 9*Mau23 + 6*Meu1 + (6*I)*Meu2)/Sqrt[14], k == 4 && m == 3}, {(-13*Sqrt[33/7]*(Eau1 - Eau3 - (2*I)*Mau13))/20, k == 6 && m == -6}, {(13*Sqrt[3/14]*(I*Mau12 + Mau23 - 3*Meu1 + (3*I)*Meu2))/5, k == 6 && m == -3}, {(-13*(Eau1 - 20*Eau2 + Eau3 + 30*Eeu1 - 12*Eeu2))/140, k == 6 && m == 0}, {(13*Sqrt[3/14]*(I*Mau12 - Mau23 + 3*Meu1 + (3*I)*Meu2))/5, k == 6 && m == 3}, {(-13*Sqrt[33/7]*(Eau1 - Eau3 + (2*I)*Mau13))/20, k == 6 && m == 6}}, 0]