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3 of 10 MathJaxed chemistry

How many $Ga$ atoms are connected to one $As$ atom in solid state Gallium arsenide

Let's start straight away. In this book on page 4 Gallium arsenide's bond structure is shown like this:
image 1
$As$ is shown making $5$ covalent bonds.
Recently I came across this book. The bond structure of $\ce{GaAs}$ is shown like this:
image 2.

Here $\ce{As}$ is shown to make $4$ covalent bonds. For sure one of the above quoted images is wrong. But which?

To how many $\ce{Ga}$ atoms one $\ce{As}$ atom is connected? Actually. Please explain your answer with established reference(s) and also give experimental proof in your answer that supports your answer.