Help with expansion joints on Herringbone floor

[Lexter]

Dear all,
I'm half way through tiling 40sqm of an extension. It's over an existing floor which I've laid underfloor heating insulated panels and going onto the extension where it's also under floor heating but a liquid screed has been laid on top.
So it's two totally different surfaces which will also heat up differently.
I'm after a solution for having a continuous flow of tiles without having a break in it as it would be really notifiable. It's all open planned.
Could I use sealant as a break? From one side to the other where the floor meets. I can easily get a matching colour for the grout and it would not be that noticeable?
As always your superior knowledge has been invaluable and although I don't post alot most of all my questions has been asked already and a searched avoids repeated questions.
Thanks for your time.

 

[Qwerty]

Yes, colour matching Silicon in a straight line following the divide of the two substrates is the way to go.

 

[Lexter]

Many thanks for quick response!!

 

[Danielle]

Many thanks for quick response!!

Hi Lexter

Do you have a photo of the finished product with the Silicon join?

We have the same issue

 

[akis_t]

Hi, as you were laying down the floor, how did you ensure it is all "square"? Did you mark it before hand or did you lay the boards and let them guide you?