hush, you'll spoil it.
Teryons are multidimensional energy units, reaching into multiple quantum states. They exist everywhere and in every state in equal capacity. I think that qualifies as a type of energy shield that can oppose an MPAC, because an MPAC projectile doesn't have any quantum states that are unopposed by the shield.
It'll still pack one hell of a punch, though. Stopping a metaphased energy weapon takes a tremendous amount of power, cause your shield generator has to power spike across a vast spectrum. That's a serious power drain.
So yes, the Scimitar's shields can't be penetrated by any weapon that is usually shield piercing, but stopping a shield-piercing weapon isn't something a shield can do all day. Even a teryon shield won't stand up to major punishment for long (the Karinnes were still in what you might call the first stages of teryon shield research). It'll overheat and go down very quickly.
It's not the shields that are gonna give Trillane fits, though...it's the armor.
Compressed Neutronium Armor is crystallized neutronium (neutronium whose molecular structure is altered into a diamond-like tetrahedral crystalline form) that is exposed to a singularity, a miniature black hole. This exposure crushes it, reducing its volume by 65%, and completely closing any molecular anomolies that a weapon might exploit to breach the armor. It's like a hull made of something so hard that diamonds would shatter against it like glass.
This tempering process creates metal that retains the same mass, and is virtually indestructible. It also cannot be bent, changed, or otherwise altered, so the armor has to be pre-cast in an expanded (ballooned) form, shrunk down, and then fitted into place. So, some very exacting precision is required, and even this isn't enough to make this technology totally reliable. The failure rate in the crushing process is 30% due to the Heisenburg Principle, which states that it is impossible to predict the exact location of an atom at a particular instant in time. If too many atoms are out of place when the exposure begins, the neutronium doesn't crush uniformly, and the armor piece is ruined. This margin of error makes the crush unreliable, and creates quite a few failures. The Karinnes tried to reduce this problem as much as they could by supercooling the armor pieces before crushing to reduce molecular vibration, but even the Karinnes couldn't get something to absolute zero (the point where all molecular vibration stops, which would eliminate the Heisenburg Principle from the equation) and keep it there long enough to get that ultra-cold armor into the singularity compressor.
And DON'T pick this apart. Yah, I know you guys can probably throw a slough of "what ifs" at this, but this is SCIENCE FICTION, damn you, you nitpickers! It works that way cause I say so, and THIS IS MY SAND BOX!