Invoice from Structural Engineer

Good day everyone,

we had our house planned by an architect.
The price included [Statik], which is also listed that way on the cost statement.

Unfortunately, the collaboration with our architect was a complete disaster (I don't want to go into details),
which is why we have not yet paid the final installment.

In addition, we have now received an invoice from the [Statiker].
We had no prior contact with this person and did not even know who was doing the [Statik].

Now my question:
Is it normal for the invoice from the [Statiker] to come to us?
We have never spoken to this person before, let alone given them an order.

As I understand it, the [Statiker] must collect the money from the architect, or am I mistaken?

Thank you in advance for your help!

if it has been agreed in the listing = contract (?) the architect must pay the structural engineer!

Have any powers of attorney been given to the architect so that he can place orders on your behalf??

Unfortunately, there is no contract as such, only the cost breakdown.

Were any powers of attorney given to the architect to award contracts on your behalf??

No, he has not received any power of attorney.

Have you talked to the structural engineer and asked what the architect agreed with him? I mean, if you don't pay, then he can't pay him either, why should the architect stick to your arrangement if you don't? It may be that you are not satisfied, but if he has done everything he owes you, then it is also his means to put pressure on you. Equal rights for both parties.

Take a look at the cost breakdown. Are there any other non-fee-related costs included (soil survey, surveying, fees...)?
With the awarding of the contract in the form of planning phases to the architect, it is clear that the associated costs will be incurred and the architect will coordinate and take the lead in commissioning them. This naturally includes the structural engineer. And the invoice goes to you, as it is not part of the architect's fee – unless explicitly regulated otherwise (uncommon). You also wouldn’t withhold the building authority’s approval fees and hold the architect liable for them.