Matrix t2*K(2) in Subspace 28 with Dimension 8

(K(2) is the second-order Grosse operator)

(-9*t*U)/2 -U^2/2 0 (3*t*U)/2 t*U 0 -(Sqrt[3]*t*U)/2 t^2*(-4 + U^2/(2*t^2))
-U^2/2 (-3*t*U)/2 (Sqrt[3]*t*U)/2 -2*t^2 0 -2*t*U 2*Sqrt[3]*t^2 -(t*U)/2
0 (Sqrt[3]*t*U)/2 (-3*t*U)/2 -(Sqrt[3]*(4*t^2 + U^2))/2 0 -(Sqrt[3]*t*U) t^2*(-2 + U^2/(2*t^2)) (3*Sqrt[3]*t*U)/2
(3*t*U)/2 -2*t^2 -(Sqrt[3]*(4*t^2 + U^2))/2 0 0 0 -2*Sqrt[3]*t*U 0
t*U 0 0 0 -2*t*U 4*t^2 0 0
0 -2*t*U -(Sqrt[3]*t*U) 0 4*t^2 -5*t*U 0 -2*t*U
-(Sqrt[3]*t*U)/2 2*Sqrt[3]*t^2 t^2*(-2 + U^2/(2*t^2)) -2*Sqrt[3]*t*U 0 0 -6*t*U 0
t^2*(-4 + U^2/(2*t^2)) -(t*U)/2 (3*Sqrt[3]*t*U)/2 0 0 -2*t*U 0 (-7*t*U)/2