Matrix t2*K(2) in Subspace 81 with Dimension 8

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

-6*t*U -(Sqrt[2]*t*U) 2*Sqrt[2]*t^2 t*U -(Sqrt[2]*t*U) -2*t^2 0 -2*t^2
-(Sqrt[2]*t*U) -4*t*U -U^2 0 0 0 4*t^2 0
2*Sqrt[2]*t^2 -U^2 (-11*t*U)/2 (4*t^2 + U^2)/Sqrt[2] 0 -((t*U)/Sqrt[2]) 0 Sqrt[2]*t*U
t*U 0 (4*t^2 + U^2)/Sqrt[2] -5*t*U -((t*U)/Sqrt[2]) 2*t^2 0 2*t^2
-(Sqrt[2]*t*U) 0 0 -((t*U)/Sqrt[2]) (-7*t*U)/2 -((4*t^2 + U^2)/Sqrt[2]) -U^2 2*Sqrt[2]*t^2
-2*t^2 0 -((t*U)/Sqrt[2]) 2*t^2 -((4*t^2 + U^2)/Sqrt[2]) -4*t*U 0 t*U
0 4*t^2 0 0 -U^2 0 -5*t*U Sqrt[2]*t*U
-2*t^2 0 Sqrt[2]*t*U 2*t^2 2*Sqrt[2]*t^2 t*U Sqrt[2]*t*U -3*t*U