Matrix t2*K(2) in Subspace 80 with Dimension 8

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

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